diff --git a/resources/build/bootstrap-ubuntu-20.04.sh b/resources/build/bootstrap-ubuntu-20.04.sh
index 25bbe67f1..f94086633 100644
--- a/resources/build/bootstrap-ubuntu-20.04.sh
+++ b/resources/build/bootstrap-ubuntu-20.04.sh
@@ -10,13 +10,14 @@ sudo apt-get install -y build-essential pkgconf clang-format-12 clang-tidy-12 py
 # These would be installed as part of the conan package install, but
 # we're caching the conan directory via the `actions/cache` Github
 # action, so a fresh Github VM is left without these system packages.
-sudo apt-get install -y  --no-install-recommends libfontenc-dev libx11-xcb-dev libxaw7-dev \
-    libxcb-dri3-dev libxcb-icccm4-dev libxcb-image0-dev libxcb-keysyms1-dev libxcb-randr0-dev \
-    libxcb-render-util0-dev libxcb-shape0-dev libxcb-sync-dev libxcb-util-dev libxcb-xfixes0-dev \
-    libxcb-xinerama0-dev libxcb-xkb-dev libxcomposite-dev libxcursor-dev libxdamage-dev \
-    libxfixes-dev libxi-dev libxinerama-dev libxmu-dev libxmuu-dev libxpm-dev libxrandr-dev \
-    libxres-dev libxss-dev libxtst-dev libxv-dev libxvmc-dev libxxf86vm-dev uuid-dev \
-    libxkbfile-dev
+sudo apt-get install -y --no-install-recommends libfontenc-dev libice-dev libsm-dev libx11-dev \
+ libx11-xcb-dev libxau-dev libxaw7-dev libxcb-dri3-dev libxcb-icccm4-dev libxcb-image0-dev \
+ libxcb-keysyms1-dev libxcb-randr0-dev libxcb-render0-dev libxcb-render-util0-dev \
+ libxcb-shape0-dev libxcb-sync-dev libxcb-util-dev libxcb-xfixes0-dev libxcb-xinerama0-dev \
+ libxcb-xkb-dev libxcomposite-dev libxcursor-dev libxdamage-dev libxdmcp-dev libxext-dev \
+ libxfixes-dev libxi-dev libxinerama-dev libxkbfile-dev libxmu-dev libxmuu-dev libxpm-dev \
+ libxrandr-dev libxrender-dev libxres-dev libxss-dev libxt-dev libxtst-dev libxv-dev libxvmc-dev \
+ libxxf86vm-dev uuid-dev xkb-data xtrans-dev
 
 # Install additional build tools.
 sudo pip3 install -r "$WORKSPACE/resources/build/requirements.txt"
@@ -32,7 +33,14 @@ conan profile new default --detect --force
 conan profile update settings.compiler.libcxx=libstdc++ default
 # Install openassetio third-party dependencies from public Conan Center
 # package repo.
+# TODO(DF): conan<1.51 (not yet released) has a bug that means we have
+# to allow conan recipes to try to install system packages, even if the
+# system packages are already available. In particular, this affects
+# recent versions of the xorg/system recipe (a dependency of cpython).
+# The problem is reported and fixed in https://github.com/conan-io/conan/pull/11712
 conan install --install-folder "$CONAN_USER_HOME" --build=missing \
+    -c tools.system.package_manager:mode=install \
+    -c tools.system.package_manager:sudo=True \
     "$WORKSPACE/resources/build"
 # Ensure we have the expected version of clang-* available
 sudo update-alternatives --install /usr/bin/clang-tidy clang-tidy /usr/bin/clang-tidy-12 10
diff --git a/resources/build/requirements.txt b/resources/build/requirements.txt
index 0017e9f17..b58599f61 100644
--- a/resources/build/requirements.txt
+++ b/resources/build/requirements.txt
@@ -1,4 +1,4 @@
-conan==1.48.1
+conan==1.50.0
 cmake==3.21
 ninja==1.10.2.3
 cpplint==1.5.5