Boris Johnson has been warned he could trigger the “gravest” constitutional crisis since Charles I if he refused to resign after losing a vote of no confidence, as a prominent businesswoman threatened a judicial review.

The Tory leadership candidate said MPs would set up parliament outside the Palace of Westminster if the frontrunner for PM tried to lock them out. / Tory leadership candidate Rory Stewart has said he will “bring down” front-runner Boris Johnson as prime minister if he tries to suspend parliament to force through a no-deal Brexit.