Two teenagers have been arrested after former British ambassador to the US Sir Christopher Meyer was attacked.
His wife, Baroness Meyer, said the 74-year-old is in hospital being treated for injuries "like something you would see in a war zone" after being set upon at Victoria Underground station in central London.
British Transport Police (BTP) said a 15-year-old girl and a boy aged 16 have been arrested on suspicion of assault occasioning grievous bodily harm after the attack at around 2.45pm on Wednesday.
Lady Meyer told the Times: "He looks terrible. His left eye is like a golf ball and bleeding, the nose looks like it could be broken.
"I'm absolutely shocked by the level of the brutality. They really beat him. It's appalling - like something you would see in a war zone."
A picture showed Sir Christopher, who was the UK's ambassador to the US between 1997 and 2003, covered in blood while lying in a hospital bed.
The attack came ahead of US President Donald Trump's visit to the UK, and the former diplomat was reportedly due to give television interviews to discuss the event.
A BTP statement called for witnesses to come forward and said his injuries "are not believed to be life-threatening or changing".
The boy, from Hillingdon, north-west London, and the girl, from Croydon, south London, have been released under investigation, the BTP said.