The European Union will delay Brexit until February if Boris Johnson is unable to get his deal past MPs this week.

Diplomatic sources said that the delay would be “fungible” meaning that Britain could leave earlier, on the 1st or 15th of November, December or January, if his deal is ratified before the extension ends.

No decision will be taken until EU governments can assess the chances of the withdrawal treaty getting through parliament, not before Tuesday this week. If the prime minister runs into serious trouble or MPs force a second referendum then countries led by Germany will push for a longer extension, possibly until June next year.