The end of the political road for David Cameron

Credit: Reuters

David Cameron was in a reflective mood today, writes ITV News deputy political editor Chris Ship.

He was after all announcing the end of his career in British politics after quitting as the Tory MP for Witney.

He said it was a 'sad day' as we met in his constituency moments after he'd told Prime Minister Theresa May of his decision.

Just a few months ago, he was the man in charge at Number 10 and fighting to keep the UK in the European Union.

It was to be an endeavour which ended in failure.

But Mr Cameron had always said he would stay as the Member of Parliament for Witney if he ever did leave Downing Street.

Today, he tried to explain how that was no longer possible.

He said he wasn't able to be a 'full constituency MP' because his former job - as Prime Minister - meant he would not be free to speak on issues without being a major distraction to Mrs May.

I asked him - as a former opponent of grammar school expansion - if his decision was connected to Mrs May's speech three days ago.

He said the timing was mere 'coincidence' - but neither would he tell me that he fully supports Mrs May's policy of allowing more schools to select by ability.

And he doesn't like the proposals to allow faith schools to admit more pupils on religious grounds.

And that perhaps goes to the heart of the problem: how is it possible to be a backbench MP when you have just left the office of Prime Minister?

Cameron said he did not want to detract from the work of May's government Credit: PA

I'm told by friends of Mr Cameron that he might have made this decision sooner - had the Tory leadership election run its full course over the summer.

But the sudden election of Theresa May as the new Tory leader didn't give him that period of reflection.

Tony Blair cleared out when Gordon Brown took over.

But as former Prime Ministers from Ted Heath to Margaret Thatcher will testify, they're often seen to be breathing down their successor's back.

The by-election in Witney will be a shoe-in for the Tory candidate but what will Mr Cameron do next?

He insists he doesn't have any plans - although many will expect him to line up something more lucrative than the £74,000 salary of an MP.

He says he wants to do something connected to some of the causes he championed as Prime Minister.

But his time in British politics has just come to an end.