On 25 September, John McDonnell told the Guardian that Labour would support Osborne’s fiscal charter:

“We accept we are going to have to live within our means and we always will do – full stop. We are not deficit deniers. We will support the charter. We will support the charter on the basis we are going to want to balance the books, we do want to live within our means and we will tackle the deficit.”

Today, 17 days later, McDonnell writes to Labour MPs telling them to vote against:

“I believe that we need to underline our position as an anti-austerity party by voting against the Charter on Wednesday. We will rebuff any allegation of being deficit deniers by publishing for the debate our own statement on budget responsibility. We will set out our plan for tackling the deficit not through punishing the most vulnerable and decimiating our public services but by ending the unfair tax cuts to the wealthy, tackling tax evasion and investing for growth.” 

Did Momentum get to him?