diff --git a/.cirrus.yml b/.cirrus.yml
index 971bd3b81b..007bab403e 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -107,7 +107,7 @@ linux_minimal_task:
   tests_script:
     - echo "[Resources]" > ${SITE_CFG}
     - echo "doc_dir = ${CIRRUS_WORKING_DIR}/docs" >> ${SITE_CFG}
-    - nox --session tests
+    - nox --session tests -- --verbose
 
 
 #
@@ -137,7 +137,7 @@ linux_task:
     - echo "[Resources]" > ${SITE_CFG}
     - echo "test_data_dir = ${IRIS_TEST_DATA_DIR}/test_data" >> ${SITE_CFG}
     - echo "doc_dir = ${CIRRUS_WORKING_DIR}/docs" >> ${SITE_CFG}
-    - nox --session tests
+    - nox --session tests -- --verbose
 
 
 #
@@ -167,7 +167,7 @@ gallery_task:
     - echo "[Resources]" > ${SITE_CFG}
     - echo "test_data_dir = ${IRIS_TEST_DATA_DIR}/test_data" >> ${SITE_CFG}
     - echo "doc_dir = ${CIRRUS_WORKING_DIR}/docs" >> ${SITE_CFG}
-    - nox --session gallery
+    - nox --session gallery -- --verbose
 
 
 #
@@ -201,7 +201,7 @@ doctest_task:
     - mkdir -p ${MPL_RC_DIR}
     - echo "backend : agg" > ${MPL_RC_FILE}
     - echo "image.cmap : viridis" >> ${MPL_RC_FILE}
-    - nox --session doctest
+    - nox --session doctest -- --verbose
 
 
 #
@@ -224,4 +224,4 @@ link_task:
     - mkdir -p ${MPL_RC_DIR}
     - echo "backend : agg" > ${MPL_RC_FILE}
     - echo "image.cmap : viridis" >> ${MPL_RC_FILE}
-    - nox --session linkcheck
+    - nox --session linkcheck -- --verbose
diff --git a/docs/src/developers_guide/contributing_running_tests.rst b/docs/src/developers_guide/contributing_running_tests.rst
index 99ea4e831c..0fd9fa8486 100644
--- a/docs/src/developers_guide/contributing_running_tests.rst
+++ b/docs/src/developers_guide/contributing_running_tests.rst
@@ -175,6 +175,14 @@ For further `nox`_ command-line options::
 
   nox --help
 
+.. tip::
+    For `nox`_ sessions that use the `conda`_ backend, you can use the ``-v`` or ``--verbose``
+    flag to display the `nox`_ `conda`_ environment package details and environment info.
+    For example::
+
+        nox --session tests -- --verbose
+
+
 .. note:: `nox`_ will cache its testing environments in the `.nox` root ``iris`` project directory.
 
 
diff --git a/docs/src/whatsnew/latest.rst b/docs/src/whatsnew/latest.rst
index fbb98cb1e3..ed11f60719 100644
--- a/docs/src/whatsnew/latest.rst
+++ b/docs/src/whatsnew/latest.rst
@@ -94,6 +94,10 @@ This document explains the changes made to Iris for this release
 
 #. `@jamesp`_ updated a test to the latest numpy version (:pull:`3977`)
 
+#. `@bjlittle`_ rationalised the ``noxfile.py``, and added the ability for
+   each ``nox`` session to list its ``conda`` environment packages and
+   environment info. (:pull:`3990`)
+
 
 .. comment
     Whatsnew author names (@github name) in alphabetical order. Note that,
diff --git a/noxfile.py b/noxfile.py
index fc6175bdf0..b6f9480290 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -93,6 +93,58 @@ def cache_cartopy(session):
         )
 
 
+def prepare_venv(session):
+    """
+    Create and cache the nox session conda environment, and additionally
+    provide conda environment package details and info.
+
+    Note that, iris is installed into the environment using pip.
+
+    Parameters
+    ----------
+    session: object
+        A `nox.sessions.Session` object.
+
+    Notes
+    -----
+    See
+      - https://github.com/theacodes/nox/issues/346
+      - https://github.com/theacodes/nox/issues/260
+
+    """
+    if not venv_cached(session):
+        # Determine the conda requirements yaml file.
+        fname = f"requirements/ci/py{session.python.replace('.', '')}.yml"
+        # Back-door approach to force nox to use "conda env update".
+        command = (
+            "conda",
+            "env",
+            "update",
+            f"--prefix={session.virtualenv.location}",
+            f"--file={fname}",
+            "--prune",
+        )
+        session._run(*command, silent=True, external="error")
+        cache_venv(session)
+
+    cache_cartopy(session)
+    session.install("--no-deps", "--editable", ".")
+
+    # Determine whether verbose diagnostics have been requested
+    # from the command line.
+    verbose = "-v" in session.posargs or "--verbose" in session.posargs
+
+    if verbose:
+        session.run("conda", "info")
+        session.run("conda", "list", f"--prefix={session.virtualenv.location}")
+        session.run(
+            "conda",
+            "list",
+            f"--prefix={session.virtualenv.location}",
+            "--explicit",
+        )
+
+
 @nox.session
 def flake8(session):
     """
@@ -141,30 +193,8 @@ def tests(session):
     session: object
         A `nox.sessions.Session` object.
 
-    Notes
-    -----
-    See
-      - https://github.com/theacodes/nox/issues/346
-      - https://github.com/theacodes/nox/issues/260
-
     """
-    if not venv_cached(session):
-        # Determine the conda requirements yaml file.
-        fname = f"requirements/ci/py{session.python.replace('.', '')}.yml"
-        # Back-door approach to force nox to use "conda env update".
-        command = (
-            "conda",
-            "env",
-            "update",
-            f"--prefix={session.virtualenv.location}",
-            f"--file={fname}",
-            "--prune",
-        )
-        session._run(*command, silent=True, external="error")
-        cache_venv(session)
-
-    cache_cartopy(session)
-    session.install("--no-deps", "--editable", ".")
+    prepare_venv(session)
     session.run(
         "python",
         "-m",
@@ -184,30 +214,8 @@ def gallery(session):
     session: object
         A `nox.sessions.Session` object.
 
-    Notes
-    -----
-    See
-      - https://github.com/theacodes/nox/issues/346
-      - https://github.com/theacodes/nox/issues/260
-
     """
-    if not venv_cached(session):
-        # Determine the conda requirements yaml file.
-        fname = f"requirements/ci/py{session.python.replace('.', '')}.yml"
-        # Back-door approach to force nox to use "conda env update".
-        command = (
-            "conda",
-            "env",
-            "update",
-            f"--prefix={session.virtualenv.location}",
-            f"--file={fname}",
-            "--prune",
-        )
-        session._run(*command, silent=True, external="error")
-        cache_venv(session)
-
-    cache_cartopy(session)
-    session.install("--no-deps", "--editable", ".")
+    prepare_venv(session)
     session.run(
         "python",
         "-m",
@@ -226,30 +234,8 @@ def doctest(session):
     session: object
         A `nox.sessions.Session` object.
 
-    Notes
-    -----
-    See
-      - https://github.com/theacodes/nox/issues/346
-      - https://github.com/theacodes/nox/issues/260
-
     """
-    if not venv_cached(session):
-        # Determine the conda requirements yaml file.
-        fname = f"requirements/ci/py{session.python.replace('.', '')}.yml"
-        # Back-door approach to force nox to use "conda env update".
-        command = (
-            "conda",
-            "env",
-            "update",
-            f"--prefix={session.virtualenv.location}",
-            f"--file={fname}",
-            "--prune",
-        )
-        session._run(*command, silent=True, external="error")
-        cache_venv(session)
-
-    cache_cartopy(session)
-    session.install("--no-deps", "--editable", ".")
+    prepare_venv(session)
     session.cd("docs")
     session.run(
         "make",
@@ -274,30 +260,8 @@ def linkcheck(session):
     session: object
         A `nox.sessions.Session` object.
 
-    Notes
-    -----
-    See
-      - https://github.com/theacodes/nox/issues/346
-      - https://github.com/theacodes/nox/issues/260
-
     """
-    if not venv_cached(session):
-        # Determine the conda requirements yaml file.
-        fname = f"requirements/ci/py{session.python.replace('.', '')}.yml"
-        # Back-door approach to force nox to use "conda env update".
-        command = (
-            "conda",
-            "env",
-            "update",
-            f"--prefix={session.virtualenv.location}",
-            f"--file={fname}",
-            "--prune",
-        )
-        session._run(*command, silent=True, external="error")
-        cache_venv(session)
-
-    cache_cartopy(session)
-    session.install("--no-deps", "--editable", ".")
+    prepare_venv(session)
     session.cd("docs")
     session.run(
         "make",