A video that senior Labor sources had previously said didn't exist has been found by the Sun.

The video, of a conversation between Tony Blair and Gordon Brown in the aftermath of the John Smith death, clearly shows Tony Blair promising to hand over the Premiership to Gordon Brown after a second term, in return for Brown not challenging Blair for Labor leader.

The political ramifications of this discovery are immense and may bring forward Tony Blair's resignation as PM by hours, or even days.

Our political editor is down the pub but will respond later.