LONDON (Reuters) – Britain could still change its mind about Brexit after triggering its formal divorce talks with the European Union, the man who drafted Article 50 of the Lisbon Treaty told the BBC.

Prime Minister Theresa May has said she will invoke Article 50 by the end of March, kicking off two years of divorce negotiations.

“You can change your mind while the process is going on,” John Kerr, a former British ambassador to the EU who drafted Article 50, told BBC TV.

“During that period, if a country were to decide actually we don’t want to leave after all, everybody would be very cross about it being a waste of time,” he said. “They might try to extract a political price but legally they couldn’t insist that you leave.”

The High Court will rule on Thursday whether May has to get parliament’s approval before triggering Article 50, which both the claimants and the government have said is irreversible once invoked.

Attorney General Jeremy Wright, the government’s top lawyer, told the High Court last month that a notification invoking Article 50 – probably with a letter from May – was irrevocable.

Kerr, who the BBC said was advising the Scottish government, said that Article 50 was “not irrevocable”. If Article 50 could be revoked, Britain’s Brexit negotiations could be follow a significantly different path.

Kerr wants either parliament or the public – through an election or a second referendum – to revisit the decision to leave the EU in a year to 18 months time, the BBC said.

He added that if Scotland were to vote for independence, they would probably get membership of the EU pretty quickly.

“I think that when independent the Scots could apply and probably get in pretty quickly through the door marked accession,” he said.

(Reporting by Guy Faulconbridge; editing by Sarah Young)