diff --git a/benchmarks/benchmarks/experimental/ugrid/regions_combine.py b/benchmarks/benchmarks/experimental/ugrid/regions_combine.py
index 16044c663a..5ecc90930b 100644
--- a/benchmarks/benchmarks/experimental/ugrid/regions_combine.py
+++ b/benchmarks/benchmarks/experimental/ugrid/regions_combine.py
@@ -23,7 +23,7 @@
 from iris.experimental.ugrid import PARSE_UGRID_ON_LOAD
 from iris.experimental.ugrid.utils import recombine_submeshes
 
-from ... import TrackAddedMemoryAllocation
+from ... import TrackAddedMemoryAllocation, on_demand_benchmark
 from ...generate_data.ugrid import make_cube_like_2d_cubesphere
 
 
@@ -200,6 +200,8 @@ class CombineRegionsComputeRealData(MixinCombineRegions):
     def time_compute_data(self, n_cubesphere):
         _ = self.recombined_cube.data
 
+    # Vulnerable to noise, so disabled by default.
+    @on_demand_benchmark
     @TrackAddedMemoryAllocation.decorator
     def track_addedmem_compute_data(self, n_cubesphere):
         _ = self.recombined_cube.data
@@ -217,6 +219,8 @@ def time_save(self, n_cubesphere):
         # Save to disk, which must compute data + stream it to file.
         save(self.recombined_cube, "tmp.nc")
 
+    # Vulnerable to noise, so disabled by default.
+    @on_demand_benchmark
     @TrackAddedMemoryAllocation.decorator
     def track_addedmem_save(self, n_cubesphere):
         save(self.recombined_cube, "tmp.nc")
@@ -245,6 +249,8 @@ def time_stream_file2file(self, n_cubesphere):
         # Save to disk, which must compute data + stream it to file.
         save(self.recombined_cube, "tmp.nc")
 
+    # Vulnerable to noise, so disabled by default.
+    @on_demand_benchmark
     @TrackAddedMemoryAllocation.decorator
     def track_addedmem_stream_file2file(self, n_cubesphere):
         save(self.recombined_cube, "tmp.nc")
diff --git a/benchmarks/benchmarks/save.py b/benchmarks/benchmarks/save.py
index d00c66a0ca..e9a7918dcc 100644
--- a/benchmarks/benchmarks/save.py
+++ b/benchmarks/benchmarks/save.py
@@ -16,7 +16,7 @@
 from iris import save
 from iris.experimental.ugrid import save_mesh
 
-from . import TrackAddedMemoryAllocation
+from . import TrackAddedMemoryAllocation, on_demand_benchmark
 from .generate_data.ugrid import make_cube_like_2d_cubesphere
 
 
@@ -47,6 +47,8 @@ def time_netcdf_save_mesh(self, n_cubesphere, is_unstructured):
         if is_unstructured:
             self._save_mesh(self.cube)
 
+    # Vulnerable to noise, so disabled by default.
+    @on_demand_benchmark
     @TrackAddedMemoryAllocation.decorator
     def track_addedmem_netcdf_save(self, n_cubesphere, is_unstructured):
         # Don't need to copy the cube here since track_ benchmarks don't
diff --git a/docs/src/whatsnew/latest.rst b/docs/src/whatsnew/latest.rst
index b4396ad0d5..333cce6db9 100644
--- a/docs/src/whatsnew/latest.rst
+++ b/docs/src/whatsnew/latest.rst
@@ -85,6 +85,9 @@ This document explains the changes made to Iris for this release
    working properly. (Main pull request: :pull:`5437`, more detail:
    :pull:`5430`, :pull:`5431`, :pull:`5432`, :pull:`5434`, :pull:`5436`)
 
+#. `@trexfeathers`_ set a number of memory benchmarks to be on-demand, as they
+   were vulnerable to false positives in CI runs. (:pull:`5481`)
+
 #. `@acchamber`_ and `@ESadek-MO`_ resolved several deprecation to reduce
    number of warnings raised during tests.
    (:pull:`5493`, :pull:`5511`)
@@ -96,8 +99,6 @@ This document explains the changes made to Iris for this release
    longer using the ``--strict`` argument. (:pull:`5496`)
 
 
-
-
 .. comment
     Whatsnew author names (@github name) in alphabetical order. Note that,
     core dev names are automatically included by the common_links.inc: