Middleton has some regrets over the World Cup final defeat by New Zealand in November, but says he is “proud” of his work.
“Representing England in a coaching or playing capacity must be the pinnacle of any sporting career and I can’t put into words how proud and fortunate I’ve been to be able to do this for the last nine years,” he said.
“This job has created a life I’d only ever dreamt of. Hopefully, what we have managed to achieve reflects well. It means the world to me to represent my country and the RFU.
“There have been great memories built around success and great memories built around defeat. Do I regret not signing off winning the World Cup as a head coach? Yes for sure, but I know we can all live with that because we could not have worked harder or given more, sometimes that’s just not quite enough and it wasn’t on the day.
“I know last year’s World Cup campaign was and continues to be celebrated and quite rightly so – the bravery and commitment of the players in that game was exceptional and is to be admired. They are an excellent group of players, but more importantly amazing people and I know they will continue to be successful.”
England, Grand Slam champions last year, begin their Six Nations at home to Scotland on Saturday, 25 March, and end the tournament with a first standalone fixture at Twickenham against France in what is likely to be the decider.