Also, asking for a delay while a GE is held is more convincing than outright Revoke. Of course Revoke is the sensible option. But the correct forms need to be observed, and that means going through a PV before getting to Revoke.

Corbyn's position is complicated. Coming out as an outright Remain party would be electoral suicide - not by much, but certainly by enough to guarantee that the next election wouldn't just be lost, but would be lost by a large enough margin to make Labour irrelevant.

Of course this is exactly what Corbyn's many opponents want. Brexit is a perfect wedge issue for them, and the LibDems are happy to play their usual role of keeping Labour out of power while making promises about being The Remain Party, which are rather meaningless in practice.

Corbyn isn't helped by not being a typical career politician alpha bullshitter. He's more interested in policy than point scoring - which is very laudable, but it isn't what British voters are used to from a leader.

The bottom line is that whatever happens has to at least appear legitimate. The Right aren't particularly troubled by legitimacy, because they can always point to the original referendum result. But Remain are constrained by it, so any move towards Remain has to follow those correct forms.