diff --git a/check_dependent_project.sh b/check_dependent_project.sh
index cced864..de71ff9 100755
--- a/check_dependent_project.sh
+++ b/check_dependent_project.sh
@@ -18,7 +18,6 @@ check_dependent_project
 
 This check ensures that this project's dependents do not suffer downstream breakages from new code
 changes.
-
 "
 
 set -eu -o pipefail
@@ -39,19 +38,22 @@ github_api_token="$5"
 update_crates_on_default_branch="$6"
 
 this_repo_dir="$PWD"
+companions_dir="$this_repo_dir/companions"
 github_api="https://api.github.com"
+org_github_prefix="https://github.com/$org"
+org_crates_prefix="git+$org_github_prefix"
 
 our_crates=()
-our_crates_source="git+https://github.com/$org/$this_repo"
+our_crates_source="$org_crates_prefix/$this_repo"
 discover_our_crates() {
   # workaround for early exits not being detected in command substitution
   # https://unix.stackexchange.com/questions/541969/nested-command-substitution-does-not-stop-a-script-on-a-failure-even-if-e-and-s
   local last_line
 
-  local found
   while IFS= read -r crate; do
     last_line="$crate"
     # for avoiding duplicate entries
+    local found
     for our_crate in "${our_crates[@]}"; do
       if [ "$crate" == "$our_crate" ]; then
         found=true
@@ -63,8 +65,8 @@ discover_our_crates() {
     else
       our_crates+=("$crate")
     fi
-  # dependents with {"source": null} are the ones we own, hence the getpath($p)==null in the jq
-  # script below
+  # dependencies with {"source": null} are the ones in this project's workspace,
+  # hence the getpath($p)==null in the jq script below
   done < <(cargo metadata --quiet --format-version=1 | jq -r '
     . as $in |
     paths |
@@ -77,10 +79,11 @@ discover_our_crates() {
   fi
 }
 
-match_their_crates() {
+dependent_companions=()
+match_dependent_crates() {
   local target_name="$1"
   local crates_not_found=()
-  local found
+  dependent_companions=()
 
   # workaround for early exits not being detected in command substitution
   # https://unix.stackexchange.com/questions/541969/nested-command-substitution-does-not-stop-a-script-on-a-failure-even-if-e-and-s
@@ -101,7 +104,28 @@ match_their_crates() {
       ;;
       source)
         next="crate"
+
+        for comp in "${companions[@]}"; do
+          local companion_crate_source="$org_crates_prefix/$comp"
+          if [ "$line" == "$companion_crate_source" ] || [[ "$line" == "$companion_crate_source?"* ]]; then
+            # prevent duplicates in dependent_companions
+            local found
+            for dep_comp in "${dependent_companions[@]}"; do
+              if [ "$dep_comp" == "$comp" ]; then
+                found=true
+                break
+              fi
+            done
+            if [ "${found:-}" ]; then
+              unset found
+            else
+              dependent_companions+=("$comp")
+            fi
+          fi
+        done
+
         if [ "$line" == "$our_crates_source" ] || [[ "$line" == "$our_crates_source?"* ]]; then
+          local found
           for our_crate in "${our_crates[@]}"; do
             if [ "$our_crate" == "$crate" ]; then
               found=true
@@ -145,78 +169,156 @@ match_their_crates() {
   if [ "${crates_not_found[@]}" ]; then
     echo -e "Errors during crate matching\n"
     printf "Failed to detect our crate \"%s\" referenced in $target_name\n" "${crates_not_found[@]}"
-    echo -e "\nNote: this error generally happens if you have deleted or renamed a crate and did not update it in $target_name. Consider opening a companion pull request on $target_name and referencing it in this pull request's description like:\n$target_name companion: [your companion PR here]"
+    echo -e "\nNote: this error generally happens if you have deleted or renamed a crate and did not update it in $target_name. Consider opening a companion pull request on $target_name and referencing it in this PR's description like:\n$target_name companion: [your companion PR here]"
     die "Check failed"
   fi
 }
 
-patch_and_check_dependent() {
-  match_their_crates "$(basename "$PWD")"
-
-  # Update the crates to the latest version.
-  #
-  # This is for example needed if there was a pr to Substrate that only required a Polkadot companion
-  # and Cumulus wasn't yet updated to use the latest commit of Polkadot.
-  for update in $update_crates_on_default_branch; do
-    cargo update -p $update
-  done
-
-  diener patch --crates-to-patch "$this_repo_dir" "$this_repo_diener_arg" --path "Cargo.toml"
-  eval "${COMPANION_CHECK_COMMAND:-cargo check --all-targets --workspace}"
-}
+companions=()
+process_pr_description_line() {
+  local companion_expr="$1"
+  local source="$2"
 
-process_companion_pr() {
   # e.g. https://github.com/paritytech/polkadot/pull/123
   # or   polkadot#123
-  local companion_expr="$1"
   if
     [[ "$companion_expr" =~ ^https://github\.com/$org/([^/]+)/pull/([[:digit:]]+) ]] ||
     [[ "$companion_expr" =~ ^$org/([^#]+)#([[:digit:]]+) ]] ||
-    [[ "$companion_expr" =~ ^([^#]+)#([[:digit:]]+) ]]; then
-    local companion_repo="${BASH_REMATCH[1]}"
-    local companion_pr_number="${BASH_REMATCH[2]}"
-    echo "Parsed companion_repo=$companion_repo and companion_pr_number=$companion_pr_number from $companion_expr (trying to match companion_repo=$dependent_repo)"
+    [[ "$companion_expr" =~ ^([^#]+)#([[:digit:]]+) ]]
+  then
+    local repo="${BASH_REMATCH[1]}"
+    local pr_number="${BASH_REMATCH[2]}"
+    echo "Parsed companion repo=$repo and pr_number=$pr_number in $companion_expr from $source"
+
+    if [ "$this_repo" == "$repo" ]; then
+      echo "Skipping $companion_expr as it refers to the repository where this script is currently running"
+      return
+    fi
+
+    # keep track of duplicated companion references not only to avoid useless
+    # work but also to avoid infinite mutual recursion when 2+ PRs reference
+    # each other
+    for comp in "${companions[@]}"; do
+      if [ "$comp" == "$repo" ]; then
+        echo "Skipping $companion_expr as the repository $repo has already been registered before"
+        return
+      fi
+    done
+    companions+=("$repo")
+
+    # Heuristic: assume the companion PR has a common merge ancestor with master
+    # in its last N commits.
+    local merge_ancestor_max_depth=100
+
+    # Clone the default branch of this companion's target repository (assumed to
+    # be named "master")
+    git clone \
+      --depth=$merge_ancestor_max_depth \
+      "https://github.com/$org/$repo.git" \
+      "$companions_dir/$repo"
+    pushd "$companions_dir/$repo" >/dev/null
+
+    # Clone the companion's branch
+    local ref="$(curl \
+        -sSL \
+        -H "Authorization: token $github_api_token" \
+        "$github_api/repos/$org/$repo/pulls/$pr_number" | \
+      jq -e -r ".head.ref"
+    )"
+    git fetch --depth=$merge_ancestor_max_depth origin "pull/$pr_number/head:$ref"
+    git checkout "$ref"
+
+echo "
+Attempting to merge $repo#$pr_number with master after fetching its last $merge_ancestor_max_depth commits.
+
+If this step fails, either:
+
+- $repo#$pr_number has conflicts with master
+
+OR
+
+- A common merge ancestor could not be found between master and the last $merge_ancestor_max_depth commits of $repo#$pr_number.
+
+Both cases can be solved by merging master into $repo#$pr_number.
+"
+    git show-ref origin/master
+    git merge origin/master \
+      --verbose \
+      --no-edit \
+      -m "Merge master of $repo into companion $repo#$pr_number"
+
+    popd >/dev/null
+
+    # collect also the companions of companions
+    process_pr_description "$repo" "$pr_number"
   else
-    die "Companion PR description had invalid format or did not belong to organization $org: $companion_expr"
+    die "Companion in the PR description of $source had invalid format or did not belong to organization $org: $companion_expr"
   fi
+}
 
-  if [ "$companion_repo" != "$dependent_repo" ]; then
-    echo "companion repo $companion_repo doesn't match dependent repo $dependent_repo. Check that you pasted the pure link to the companion."
+process_pr_description() {
+  local repo="$1"
+  local pr_number="$2"
+
+  if ! [[ "$pr_number" =~ ^[[:digit:]]+$ ]]; then
     return
   fi
 
-  was_companion_found=true
+  echo "Processing PR $repo#$pr_number"
 
-  read -d '\n' -r mergeable pr_head_ref pr_head_sha < <(curl \
+  local lines=()
+  while IFS= read -r line; do
+    lines+=("$line")
+  done < <(curl \
       -sSL \
       -H "Authorization: token $github_api_token" \
-      "$github_api/repos/$org/$companion_repo/pulls/$companion_pr_number" | \
-    jq -r "[
-      .mergeable // error(\"Companion $companion_expr is not mergeable\"),
-      .head.ref // error(\"Missing .head.ref from API data of $companion_expr\"),
-      .head.sha // error(\"Missing .head.sha from API data of $companion_expr\")
-    ] | .[]"
-  # https://stackoverflow.com/questions/40547032/bash-read-returns-with-exit-code-1-even-though-it-runs-as-expected
-  # ignore the faulty exit code since read still is regardless still reading the values we want
-  ) || :
-
-  local expected_mergeable=true
-  if [ "$mergeable" != "$expected_mergeable" ]; then
-    die "Github API says $companion_expr is not mergeable (got $mergeable, expected $expected_mergeable)"
+      "$github_api/repos/$org/$repo/pulls/$pr_number" | \
+    jq -e -r ".body"
+  )
+  # in case the PR has no body, jq should have printed "null" which effectively
+  # means lines will always be populated with something
+  if ! [ "$lines" ]; then
+    die "No lines were read for the description of PR $pr_number (some error probably occurred)"
   fi
 
-  echo
-  echo "merging master into the pr..."
-  git clone --depth 100 "https://github.com/$org/$companion_repo.git"
-  pushd "$companion_repo" >/dev/null
-  git fetch origin "pull/$companion_pr_number/head:$pr_head_ref"
-  git checkout "$pr_head_sha"
-  git merge master --verbose --no-edit -m "master was merged into the pr by check_dependent_project.sh process_companion_pr()"
-  echo "done"
-  echo
+  for line in "${lines[@]}"; do
+    if [[ "$line" =~ [cC]ompanion:[[:space:]]*([^[:space:]]+) ]]; then
+      echo "Detected companion in the PR description of $repo#$pr_number: ${BASH_REMATCH[1]}"
+      process_pr_description_line "${BASH_REMATCH[1]}" "$repo#$pr_number"
+    fi
+  done
+}
+
+patch_and_check_dependent() {
+  local dependent="$1"
+  local dependent_repo_dir="$2"
+
+  pushd "$dependent_repo_dir" >/dev/null
+
+  match_dependent_crates "$dependent"
+
+  # Update the crates to the latest version. This is for example needed if there
+  # was a PR to Substrate which only required a Polkadot companion and Cumulus
+  # wasn't yet updated to use the latest commit of Polkadot.
+  for update in $update_crates_on_default_branch; do
+    cargo update -p "$update"
+  done
+
+  for comp in "${dependent_companions[@]}"; do
+    echo "Patching $comp companion into $dependent"
+    diener patch \
+      --target "$org_github_prefix/$comp" \
+      --crates-to-patch "$companions_dir/$comp" \
+      --path "Cargo.toml"
+  done
+
+  echo "Patching $this_repo into $dependent"
+  diener patch \
+    --target "$org_github_prefix/$this_repo" \
+    --crates-to-patch "$this_repo_dir" \
+    --path "Cargo.toml"
 
-  echo "running checks for the companion $companion_expr of $companion_repo"
-  patch_and_check_dependent
+  eval "${COMPANION_CHECK_COMMAND:-cargo check --all-targets --workspace}"
 
   popd >/dev/null
 }
@@ -227,77 +329,33 @@ main() {
   git config --global user.email '<>'
   git config --global pull.rebase false
 
-  echo
-  echo "merging master into the pr..."
-  # Merge master into our branch so that the compilation takes into account how the code is going to
-  # perform when the code for this pull request lands on the target branch (à la pre-merge pipelines).
-  # Note that the target branch might not actually be master, but we default to it in the assumption
-  # of the common case. This could be refined in the future.
-  git fetch origin +master:master
-  git fetch origin +$CI_COMMIT_REF_NAME:$CI_COMMIT_REF_NAME
-  git checkout $CI_COMMIT_REF_NAME
-  git merge master --verbose --no-edit -m "master was merged into the pr by check_dependent_project.sh main()"
-  echo "done"
-  echo
+  # Merge master into this branch so that we have a better expectation of the
+  # integration still working after this PR lands.
+  # Since master's HEAD is being merged here, at the start the dependency chain,
+  # the same has to be done for all the companions because they might have
+  # accompanying changes for the code being brought in.
+  git fetch --force origin master
+  git show-ref origin/master
+  echo "Merge master into $CI_COMMIT_REF_NAME"
+  git merge origin/master \
+    --verbose \
+    --no-edit \
+    -m "Merge master into $CI_COMMIT_REF_NAME"
 
   discover_our_crates
 
-  if [[ "$CI_COMMIT_REF_NAME" =~ ^[[:digit:]]+$ ]]; then
-    echo "this is pull request number $CI_COMMIT_REF_NAME"
-
-    # workaround for early exits not being detected in command substitution
-    # https://unix.stackexchange.com/questions/541969/nested-command-substitution-does-not-stop-a-script-on-a-failure-even-if-e-and-s
-    local last_line
-
-    while IFS= read -r line; do
-      last_line="$line"
-
-      if [[ "$line" =~ [cC]ompanion:[[:space:]]*([^[:space:]]+) ]]; then
-        echo "Detected companion in PR description: ${BASH_REMATCH[1]}"
-        process_companion_pr "${BASH_REMATCH[1]}"
-      elif [[ "$line" =~ skip[^[:alnum:]]+([^[:space:]]+) ]]; then
-        # FIXME: This escape hatch should be removed at some point when the
-        # companion build system is able to deal with all edge cases, such as
-        # the one described in
-        # https://github.com/paritytech/pipeline-scripts/issues/3#issuecomment-947539791
-        if [[
-          "${BASH_REMATCH[1]}" = "$CI_JOB_NAME" ||
-          "${BASH_REMATCH[1]}" = "continuous-integration/gitlab-$CI_JOB_NAME"
-        ]]; then
-          echo "Skipping $CI_JOB_NAME as specified in the PR description"
-          exit
-        fi
-      fi
-    done < <(curl \
-        -sSL \
-        -H "Authorization: token $GITHUB_TOKEN" \
-        "$github_api/repos/$org/$this_repo/pulls/$CI_COMMIT_REF_NAME" | \
-      jq -e -r ".body"
-    )
-    if [ -z "${last_line+_}" ]; then
-      die "No lines were read for the description of PR $companion_pr_number (some error probably occurred)"
-    fi
-  fi
+  # process_pr_description calls itself for each companion in the description on
+  # each detected companion PR, effectively considering all companion references
+  # on all PRs
+  process_pr_description "$this_repo" "$CI_COMMIT_REF_NAME"
 
-  if [ "${was_companion_found:-}" ]; then
-    exit
+  local dependent_repo_dir="$companions_dir/$dependent_repo"
+  if ! [ -e "$dependent_repo_dir" ]; then
+    echo "Cloning $dependent_repo directly as it was not detected as a companion"
+    dependent_repo_dir="$this_repo_dir/$dependent_repo"
+    git clone --depth=1 "https://github.com/$org/$dependent_repo.git" "$dependent_repo_dir"
   fi
 
-  echo "running checks for the default branch of $dependent_repo"
-
-  git clone --depth 1 "https://github.com/$org/$dependent_repo.git"
-  pushd "$dependent_repo" >/dev/null
-
-  # Update the crates to the latest version.
-  #
-  # This is for example needed if there was a pr to Substrate that only required a Polkadot companion
-  # and Cumulus wasn't yet updated to use the latest commit of Polkadot.
-  for update in $update_crates_on_default_branch; do
-    cargo update -p $update
-  done
-
-  patch_and_check_dependent
-
-  popd >/dev/null
+  patch_and_check_dependent "$dependent_repo" "$dependent_repo_dir"
 }
 main