For those wondering why exactly Labour vetoed plans for a new female deputy leader this morning over fears the role could undermine Jeremy Corbyn, look no further than Emily Thornberry's conference speech. This afternoon, the shadow foreign secretary offered a pretty good explanation as to why Corbyn's allies had become nervous about the idea of promoting a woman to second in command.

Fresh from talking movingly about her backstory in a fringe event (Isabel reports on part 1 of Thornberry's leadership launch here), Thornberry gave her boss a run for his money with a crowd-pleasing – at times barnstorming – speech which neatly set out the clear blue water between herself and the current Labour leader. Thornberry received a standing ovation in the hall as she compared anti-Semites on the Left to fascists:

“ 'Conference, we must also honour the memory of the International Brigades, and lead the fight against the forces of fascism, of racism, and prejudice, and anti-semitism. Because that is what we have always done both at home and abroad, and that is what we must always do.'

Addressing Labour's anti-Semitism problem, Thornberry criticised those on the 'fringes of our movement' who use support for Palestine as a 'cloak for hatred of Jewish people'. This appears to go further than Corbyn has (unprompted) on the issue.

It was hard to watch the speech and not read leadership ambition into it. Thornberry referenced Gandhi, Martin Luther King and Robert Kennedy. She said the party 'must start with uniting' itself so that it can then focus on taking the fight to the Tories. The tricky thing for Jeremy Corbyn is that when it comes to healing wounds in Labour, Thornberry is more of a unifying figure than him. Her speech has already won praise from several different wings of the party – whether Corbyn can do the same with his tomorrow remains in the air.