Does Labour’s manifesto add up? Here’s a ConHome series to investigate – named, of course, in homage to the Shadow Home Secretary’s policing plan.

The Policy: Bringing in £6.5 billion from tax avoidance

According to Funding Britain’s Future, the Opposition’s “tax avoidance programme” will bring in £6.5 billion. This is handy, since Labour want to balance their proposed new expenditure and new revenues exactly (at £48.6 billion).

The Problem: It’s based on nonsensical figures

According to Channel 4, Labour justify their £6.5 billion figure by arguing that it splits the difference between the tax avoidance revenue predictions made by the Conservatives and Labour at the last election.

But if you think that figure is weirdly precise for so hazy an area as tax avoidance, you’re right: at the last election the Institute for Fiscal Studies accused both parties of “just making up numbers” on the subject.

So £6.5 billion is a fiction built on fictions, entirely un-anchored to any independent and realistic estimate of the likely yield of anti-avoidance measures.