diff --git a/README.md b/README.md
index f72ec20..34e29df 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,21 @@ metadata based on `git describe`.
     cd ./docker
     make
 
+## Release instructions
+
+When tagging a new version please use annotated tags in the command line
+interface.
+
+```bash
+git clone --branch master git@github.com:wtsi-npg/samtools_container.git samtools_container && cd $_
+git tag -a 'x.y.z' -m 'release x.y.z'
+git push origin x.y.z
+```
+
+Releases are created and published automatically by a GitHub Action on tag
+creation. Using the web interface to create a release will cause that
+automation to fail.
+
 # NPG Singularity wrappers
 
 Each container that provides command line programs is self-documenting
diff --git a/docker/Dockerfile b/docker/Dockerfile
index a02b129..865a7cb 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -1,7 +1,7 @@
 ARG IRODS_VERSION="4.2.11"
-ARG HTSLIB_VERSION=1.20
-ARG SAMTOOLS_VERSION=1.20
-ARG BCFTOOLS_VERSION=1.20
+ARG HTSLIB_VERSION=1.21
+ARG SAMTOOLS_VERSION=1.21
+ARG BCFTOOLS_VERSION=1.21
 ARG DEFLATE_VERSION=1.20
 
 FROM ubuntu:18.04 AS samtools_build
diff --git a/docker/Makefile b/docker/Makefile
index d896e57..a8b21fa 100644
--- a/docker/Makefile
+++ b/docker/Makefile
@@ -38,15 +38,16 @@ samtools.$(TAG): Dockerfile
 	--build-arg DOCKER_TAG=$(TAG) \
 	--build-arg IRODS_VERSION=4.2.11 \
 	--build-arg BATON_VERSION=4.2.1 \
-	--build-arg HTSLIB_VERSION=1.20 \
-	--build-arg SAMTOOLS_VERSION=1.20 \
-	--build-arg BCFTOOLS_VERSION=1.20 \
+	--build-arg HTSLIB_VERSION=1.21 \
+	--build-arg SAMTOOLS_VERSION=1.21 \
+	--build-arg BCFTOOLS_VERSION=1.21 \
 	--build-arg DEFLATE_VERSION=1.20 \
-	--label org.opencontainers.image.title="samtools" \
+	--label org.opencontainers.image.title=$(image_names) \
 	--label org.opencontainers.image.source=$(git_url) \
 	--label org.opencontainers.image.revision=$(git_commit) \
 	--label org.opencontainers.image.version=$(TAG) \
 	--label org.opencontainers.image.created=$(NOW) \
+	--label org.opencontainers.image.vendor=npg.sanger.ac.uk \
 	--tag $(DOCKER_PREFIX)/samtools:latest \
 	--tag $(DOCKER_PREFIX)/samtools:$(TAG) --file $< .
 	touch $@