Former UK PM David Cameron has stood down as an MP, triggering a by-election in his Oxfordshire seat of Witney.
Mr Cameron, 49, who resigned as prime minister after June's EU referendum, said he did not want to be a "distraction" for new PM Theresa May.
He said Mrs May had "got off to a cracking start", while she praised his "great strides" on social reform.
Speaking in his constituency, he said it had been a "great honour" to be an MP for the area, but said it would be difficult for him to remain on the backbenches without becoming "a big distraction and a big diversion" from the work of the new government.
He denied his announcement was related to the government's moves towards allowing new grammar schools, a policy he rejected as PM.
He said the timing was coincidental, adding that there were "many good things" in the proposed education reforms.
"Obviously I'm going to have my own views about different issues," he said.
"People would know that and that's really the point. As a former prime minister it is very difficult, I think, to sit as a backbencher and not be an enormous diversion and distraction from what the government is doing."
Friends say that David Cameron's decision has not been made in a fit of pique, he has not merely flounced out because he doesn't like what his successor is doing.
But there was a "very real danger", particularly because he does not support the UK leaving the European Union, that anything he said, any comment he made could "drive a real wedge" between him and the government which could make life harder for Theresa May.
It is not that surprising that the man who used to be in charge has decided to go.
Ex-Chancellor George Osborne said he was sorry his "great friend" was stepping down.