The campaign includes TV advertising for six weeks, in which Mayall plays the role of The Bombardier in an historical battle scene.
It also includes longer-form video content for the web, in-outlet activity and social media.
“Marketing in the ale category needs a creative shake-up,” said marketing director Chris Lewis.
“There are too many woolly jumpers and cosy corners that patronise our drinkers.
“Creating The Bombardier, and bringing Rik Mayall in to play him, is our way of adding some creative flair and humour to ale advertising.”