What the....?

Am I missing something? Reports in the press say that Frankie Dettori was refused permission to fly from Stanstead to Prestwick over the weekend because he didn't have his passport. Since when have you needed a passport - or for that matter any form of ID - to travel within the United Kingdom? Has Scotland become independent without telling anyone? Does this just apply to travel by air - and if so, why? Just what is going on?