A clock installed on a wall at the Conservative Party’s headquarters to count down to October 31 has been changed following the extension to the Halloween Brexit deadline.

The do-called Brexit clock now shows the amount of time since the UK “should have left the EU”.

A picture shared by Tory MP Harriett Baldwin shows the clock, now counting upwards, above which a message reads: “Time since we should have left the EU if Labour, Lib Dems and the SNP hadn’t blocked Brexit.”

The original timer was unveiled by Conservative Party chairman James Cleverly on July 31 and was displayed beneath a message which read: “We will have delivered Brexit and left the EU by.”

The digital timepiece was one of two, each reported to have cost at least £500, with the other delivered to Downing Street to be displayed in the Prime Minister’s office.

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Downing Street has confirmed that Boris Johnson will not seek any extension to the Brexit transition period if he is returned to No 10 in the General Election.

Under the Prime Minister’s proposed deal with Brussels, the UK will continue to follow EU rules after it has left the bloc until the end of 2020 to allow the two sides to negotiate a new trade deal.

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The Prime Minister’s official spokesman said the Government would not be seeking any extension to that as Mr Johnson believed there was sufficient time to get a trade deal.

“The Government will not be extending the transition period. The Prime Minister believes that we will have a good trade deal agreed with the EU by December 2020,” the spokesman said.

“The Brexit process has been going on for long enough.”

Liberal Democrat MP Angela Smith tweeted: “I seem to remember that very large numbers of Tory MPs voted against May’s deal too… including some who are now in (Boris) Johnson’s cabinet. Including Johnson himself.

“Bit of collective amnesia going on here.”