By the time of the General Election next May I will have served 26 years and 3 months as your MP.

You have supported me through thick and thin for a quarter of a century.

It will also be 20 years since I first joined the Cabinet. For 16 of those 20 years I have served as Leader of the Opposition or a member of the Cabinet or Shadow Cabinet. That is a long time to be in the political frontline.

My intention has always been that once I had completed what I set out to do as Foreign Secretary I would take a step back from the frontline and give others a chance to advance.

It will be the end of an important part of my life, but I am convinced that it is the right thing to do. I believe strongly in the old adage that it is always better to step down when people wonder why you’ve done so, than a couple of years later when they wonder why you haven’t.

I will also want to embark, after the General Election, on many other things I have always wanted to do, but am determined not to reach my mid-fifties without trying.

I will continue to campaign on issues dear to my heart, including the prevention of sexual violence in conflict, and combating the illegal wildlife trade.

I will return to my writing which gives me enormous satisfaction, but which I have set aside for the last decade.

I have had 26 extraordinarily happy, united and productive years working with you as your MP. We have repeatedly returned some of the largest majorities in the history of the constituency and at the last election the largest majority for any MP in any part of the country.

I could not have had stronger backing from my constituents, and I will continue to represent their interests and serve them until the very final moments of being an MP.

I also want to thank my wife, Ffion. She has asked me to say how much she has appreciated your support and help to her over the years.

Whoever you choose as your new candidate will have my enthusiastic backing, as my predecessors have always supported me. I will always keep a home in North Yorkshire and be ready to help.

So while I know many of you may feel some surprise at my decision, I hope that we can all join, in our very practical and forward-looking way, in making this final year of working so closely together a year of great success for our constituency, our party and our country.