Channel 4’s Dispatches will tonight air extracts from a conversation between current London mayor Boris Johnson and Old Etonian friend Darius Guppy from 1990 in which the pair discuss beating up a journalist – then News of the World reporter Stuart Collier.

In an Independent.co.uk interview in January 2007, Johnson said he had offered Guppy his help in finding the journalist because Guppy had told him ‘that some tabloid scuzzbags had reduced his family to tears’.

Listen to excerpts from the conversation at this link.

According to a statement on the Dispatches website, a spokesman for Boris Johnson said: “This was a colourful story from almost two decades ago. It was of little or no consequence back then – and has no relevance whatsoever now.”