"Ken" - one of the few politicians in the country known, often, only by his first name.
But what was familiarity also bred contempt for the arguments he made in the last two years about Hitler's alleged one-time support for Zionism.
In 2016 he said: "When Hitler won his election in 1932, his policy then was that Jews should be moved to Israel; he was supporting Zionism before he went mad and ended up killing six million Jews".
One of Jeremy Corbyn's fellow travellers, Mr Livingstone was one of the politicians on the left who'd been frozen out of Labour politics, but came back in from the cold when the Labour leader took over.
It's safe to say that although they have been friends for decades, his departure from the party will in the end have been a relief.
It seemed impossible for him to go anywhere near a microphone without repeating his controversial, and for many people, deeply offensive arguments.
Mr Corbyn wants people to believe that he is taking anti-Semitism seriously. While Mr Livingstone was still a member that was challenging to say the least.
Mr Livingstone was already being investigated by the Labour Party for his comments but, before that investigation could restart on Tuesday, he has decided to quit.
MPs suggest that he has simply decided to avoid the humiliation of almost certainly being booted out of the party he had been part of for so long.
It's clear though that although he and Mr Corbyn were fellow political travellers for years, he had long passed the point of being helpful to his old friend.
Conversations between Mr Corbyn's team and Mr Livingstone have been going on for some time, and his departure from the party crosses one awkward question off the list for the Labour leader.
But with many other cases of alleged anti-Semitism outstanding, Mr Corbyn has some way to go to prove to his critics that his promises to drive prejudice against Jewish people out of the Labour Party will be made good.