This Bbc article is missing some important details.

Piers Corbyn arrested over vaccine ‘Auschwitz leaflet’

Piers Corbyn has been arrested over leaflets comparing the UK’s Covid-19 vaccine rollout to Auschwitz. …

He was then arrested on suspicion of malicious communications and public nuisance.

The article says that he distributed leaflets, but it doesn’t actually say what he did that was a crime.