"Why on earth have you said 'yes'?" one of my close MP friends asked last night. Here's my answer. Jeremy Corbyn's win was overwhelming. He was properly nominated - by us as Labour MPs - and emphatically elected by more than 420,000 members and supporters. He is our new Labour leader. End of story. Respect for the result, means MPs need good reasons not to serve. And arguably the responsibility is greater on those of us who backed a different candidate to respond to Jeremy Corbyn's pledge to be "broad and inclusive" and a leader who "welcomes debate and wider involvement".