Theresa May suffered a fresh setback today after her civil service chief Sir Jeremy Heywood was signed off sick at a key stage in Brexit talks.
Sir Jeremy, the Cabinet Secretary and head of the Civil Service, is being treated for an infection arising from his cancer.
National security adviser Sir Mark Sedwill will take over the Cabinet Secretary role until September.
The announcement is a blow for the Prime Minister who is facing the very tricky task of trying to get her warring Cabinet and the EU to agree a Brexit deal.
And she is facing a fresh barrage of criticism from businesses who have warned they could have to leave the UK unless real progress is made in talks soon.
Sir Jeremy, the Cabinet Secretary and head of the Civil Service, is getting further treatment for his cancer, Downing Street today announced (file pic)
Airbus, which employs 14,000 people in the UK, has said itcould have to leave the UK costing many thousands of jobs if Britain crashes out of the EU without a deal.
And car giant BMW UK said the firm, which makes Minis and Rolls-Royces in Britain, demanded clarity before the summer.
He said: ‘If we don’t get clarity in the next couple of months we have to start making … contingency plans – which means investing money in systems that we might not need … which means making the UK less competitive than it is in a very competitive world right now.’
Sir Jeremy was diagnosed with cancer last June but continued to work for the PM throughout his treatment.
Sir Jeremy (pictured to the left of the PM at her first Cabinet meeting at Chequers) is a close adviser to Mrs May
The veteran civil servant was appointed to his powerful post by David Cameron in July 2014.
Sir Jeremy is a close adviser to Mrs May and often sits at her right hand during meetings.
He is one of Britain’s highest paid public servants, earning almost £200,000 – more than the Prime Minster herself.
Sir Jeremy has been a controversial figure during his tenure and branded ‘Sir Cover Up’ by critics furious at his handling of Parliamentary inquires.
He has been unpopular with Brexiteers suspicious the Civil Service is not committed to delivering on the EU referendum result.