Brexit: ‘This affects all parts and all people’
29 March 2017 Last updated at 07:39 BST
Theresa May has signed the letter triggering Article 50 and the formal process of leaving the European Union begins.
Lord Gus O'Donnell told the Today programme that in order to get the deals the UK wants we will be forced to give something in return. He said the UK is in "a plane flown by EU member states," about to jump out and they've "designed the parachutes".