diff --git a/.github/workflows/_check.yml b/.github/workflows/_check.yml
deleted file mode 100644
index a6139c19..00000000
--- a/.github/workflows/_check.yml
+++ /dev/null
@@ -1,27 +0,0 @@
-on:
-  workflow_call:
-    outputs:
-      branch-pr:
-        description: The PR number if the branch is in one
-        value: ${{ jobs.pr.outputs.branch-pr }}
-
-jobs:
-  pr:
-    runs-on: "ubuntu-latest"
-    outputs:
-      branch-pr: ${{ steps.script.outputs.result }}
-    steps:
-      - uses: actions/github-script@v7
-        id: script
-        if: github.event_name == 'push'
-        with:
-          script: |
-            const prs = await github.rest.pulls.list({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              head: context.repo.owner + ':${{ github.ref_name }}'
-            })
-            if (prs.data.length) {
-              console.log(`::notice ::Skipping CI on branch push as it is already run in PR #${prs.data[0]["number"]}`)
-              return prs.data[0]["number"]
-            }
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f198a244..463f2c79 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,22 +2,17 @@ name: CI
 
 on:
   push:
+    branches:
+      - main
   pull_request:
 
 jobs:
-  check:
-    uses: ./.github/workflows/_check.yml
-
   lint:
-    needs: check
-    if: needs.check.outputs.branch-pr == ''
     uses: ./.github/workflows/_tox.yml
     with:
       tox: pre-commit
 
   test:
-    needs: check
-    if: needs.check.outputs.branch-pr == ''
     uses: ./.github/workflows/_test.yml
     with:
       python-version: dev
@@ -26,8 +21,6 @@ jobs:
       CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
 
   docs:
-    needs: check
-    if: needs.check.outputs.branch-pr == ''
     uses: ./.github/workflows/_docs.yml
     permissions:
       contents: write
@@ -38,10 +31,3 @@ jobs:
     uses: ./.github/workflows/_example.yml
     secrets:
       EXAMPLE_DEPLOY_KEY: ${{ secrets.EXAMPLE_DEPLOY_KEY }}
-
-  release:
-    if: github.ref_type == 'tag'
-    needs: docs
-    uses: ./.github/workflows/_release.yml
-    permissions:
-      contents: write
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
new file mode 100644
index 00000000..5d22260b
--- /dev/null
+++ b/.github/workflows/release.yml
@@ -0,0 +1,31 @@
+name: CI
+
+on:
+  push:
+    tags:
+      - '*'
+
+jobs:
+  lint:
+    uses: ./.github/workflows/_tox.yml
+    with:
+      tox: pre-commit
+
+  test:
+    uses: ./.github/workflows/_test.yml
+    with:
+      python-version: dev
+      runs-on: ubuntu-latest
+    secrets:
+      CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+
+  docs:
+    uses: ./.github/workflows/_docs.yml
+    permissions:
+      contents: write
+
+  release:
+    needs: docs
+    uses: ./.github/workflows/_release.yml
+    permissions:
+      contents: write
diff --git a/docs/explanations/decisions/0021-ci-only-pr.md b/docs/explanations/decisions/0021-ci-only-pr.md
new file mode 100644
index 00000000..f5d555be
--- /dev/null
+++ b/docs/explanations/decisions/0021-ci-only-pr.md
@@ -0,0 +1,24 @@
+# 21. Run CI on pull requests and main branch only
+
+Date: 2025-05-06
+
+## Status
+
+Accepted
+
+## Context
+
+CI has been being run on branches that do not have open pull requests, which has: added spurious jobs to the organisation's compute limit; made workflow definitions more complex; made the results page harder to parse; and allowed known working development branches to become stale or forgotten.
+
+Running CI only on branches that have open pull requests will: reduce compute jobs created for code that is known to not be working; simplify workflow definitions; simplify the CI results page; encourage early creation of pull requests, adding visibility to development.
+
+Draft pull requests will still have CI jobs run, ensuring that code quality is maintained while allowing reviewers to ignore changes that are not ready for human review.
+
+## Decision
+
+CI will only be run on all PRs when changes are made, and on the main branch when PRs are merged into it: not on branches that do not have open PRs.
+Opening a draft PR will allow CI to be run, with the understanding that the PR may not be ready for review.
+
+## Consequences
+
+The `check` job will be removed and CI will run on all PRs and on the `main` branch.
diff --git "a/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/_check.yml" "b/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/_check.yml"
deleted file mode 120000
index 9c0f79a5..00000000
--- "a/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/_check.yml"	
+++ /dev/null
@@ -1 +0,0 @@
-../../../.github/workflows/_check.yml
\ No newline at end of file
diff --git "a/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/_test_all.yml" "b/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/_test_all.yml"
new file mode 100644
index 00000000..35e5d8c3
--- /dev/null
+++ "b/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/_test_all.yml"	
@@ -0,0 +1,20 @@
+on:
+  workflow_call:
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        runs-on: ["ubuntu-latest"] # can add windows-latest, macos-latest
+        python-version: ["3.10", "3.11", "3.12"]
+        include:
+          # Include one that runs in the dev environment
+          - runs-on: "ubuntu-latest"
+            python-version: "dev"
+      fail-fast: false
+    uses: ./.github/workflows/_test.yml
+    with:
+      runs-on: ${{ matrix.runs-on }}
+      python-version: ${{ matrix.python-version }}
+    secrets:
+      CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
diff --git "a/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/ci.yml.jinja" "b/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/ci.yml.jinja"
index c6ed106f..153b8e60 100644
--- "a/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/ci.yml.jinja"	
+++ "b/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/ci.yml.jinja"	
@@ -2,66 +2,32 @@ name: CI
 
 on:
   push:
+    branches:
+      - main
   pull_request:
 
 jobs:
-  check:
-    uses: ./.github/workflows/_check.yml
 
   lint:
-    needs: check
-    if: needs.check.outputs.branch-pr == ''
     uses: ./.github/workflows/_tox.yml
     with:
       tox: pre-commit,type-checking
-{% raw %}
+
   test:
-    needs: check
-    if: needs.check.outputs.branch-pr == ''
-    strategy:
-      matrix:
-        runs-on: ["ubuntu-latest"] # can add windows-latest, macos-latest
-        python-version: ["3.10", "3.11", "3.12"]
-        include:
-          # Include one that runs in the dev environment
-          - runs-on: "ubuntu-latest"
-            python-version: "dev"
-      fail-fast: false
-    uses: ./.github/workflows/_test.yml
-    with:
-      runs-on: ${{ matrix.runs-on }}
-      python-version: ${{ matrix.python-version }}
-    secrets:
-      CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
-{% endraw %}{% if docker %}
+    uses: ./.github/workflows/_test_all.yml
+
+{% if docker %}
+
   container:
-    needs: check
-    if: needs.check.outputs.branch-pr == ''
     uses: ./.github/workflows/_container.yml
     permissions:
       contents: read
       packages: write
 {% endif %}{% if sphinx %}
+
   docs:
-    needs: check
-    if: needs.check.outputs.branch-pr == ''
     uses: ./.github/workflows/_docs.yml
 {% endif %}
+
   dist:
-    needs: check
-    if: needs.check.outputs.branch-pr == ''
     uses: ./.github/workflows/_dist.yml
-  {% if pypi %}
-  pypi:
-    if: github.ref_type == 'tag'
-    needs: dist
-    uses: ./.github/workflows/_pypi.yml
-    permissions:
-      id-token: write
-  {% endif %}
-  release:
-    if: github.ref_type == 'tag'
-    needs: [dist{% if sphinx %}, docs{% endif %}]
-    uses: ./.github/workflows/_release.yml
-    permissions:
-      contents: write
diff --git "a/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/release.yml.jinja" "b/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/release.yml.jinja"
new file mode 100644
index 00000000..4a6ffc8f
--- /dev/null
+++ "b/template/{% if git_platform==\"github.com\" %}.github{% endif %}/workflows/release.yml.jinja"	
@@ -0,0 +1,49 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+
+  lint:
+    uses: ./.github/workflows/_tox.yml
+    with:
+      tox: pre-commit,type-checking
+
+  test:
+    uses: ./.github/workflows/_test_all.yml
+    with:
+      tox: pre-commit,type-checking
+{% if docker %}
+
+  container:
+    uses: ./.github/workflows/_container.yml
+    permissions:
+      contents: read
+      packages: write
+{% endif %}{% if sphinx %}
+
+  docs:
+    uses: ./.github/workflows/_docs.yml
+{% endif %}
+
+  dist:
+    uses: ./.github/workflows/_dist.yml
+{% if pypi %}
+
+  pypi:
+    if: github.ref_type == 'tag'
+    needs: dist
+    uses: ./.github/workflows/_pypi.yml
+    permissions:
+      id-token: write
+{% endif %}
+
+  release:
+    needs: [dist{% if sphinx %}, docs{% endif %}]
+    uses: ./.github/workflows/_release.yml
+    permissions:
+      contents: write