From a Guardian live feed:

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John Bercow, the Speaker of the House of Commons, has warned
Conservative leadership candidates that they will not be able to force through a no deal Brexit without parliament’s approval.
Speaking in New York, he gave a clear sign that the speaker would make sure parliament has an opportunity to stop the UK leaving without a deal if MPs believe it should be halted.
"The idea that parliament is going to be evacuated for the centre stage of debate on Brexit is simply unimaginable...The idea the House won’t have its say is for the birds," he said.
He highlighted the fact that while leaving the EU without a deal is
the legal default: "There is a difference between a legal default position and what the interplay of different political forces in parliament will facilitate."
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So much for the idea by Rabb (or perhaps just his supporters) that Parliament could be prorogued can be quietly forgotten.