"I wasn't particularly looking for a move anywhere," he says, "but West Ham had released me so I had nothing really going on.
"I got a call from Kevin Keegan and he offered the opportunity to go to a big club and play for another year while continuing my coaching education as well, so the idea quite excited me.
"I couldn't sit around and this opportunity arose so it was obviously time for me to move on."
He says he doesn't know whether he would have performed to the same level next season had he stayed in the Premiership, admitting: "I've no idea; I really couldn't say and at my age you are really on your back foot and umm-ing and ahh-ing about whether you can do it.
"But talk is quite cheap at times, though a few months ago I thought I was signing another year's contract to give it a go with Harry in the Premiership.
"I suspect I'd have been signed up at West Ham if Harry had stayed.
"But things change quickly in football and I'm looking forward to the challenge I've got ahead of me.
"Glenn has only just been put in the job just recently and by that time my future had been planned out for me because I'd given my word.
"When you get to 39 you don't have many options - I'm not Sol Campbell, I'm afraid."
He says there are no hard feelings though, adding: "I hope West Ham do well, and left a message with Glenn this week to wish him all the best, and I hope he is very successful."
He leaves on a high note, of course, having won the Hammer of the Year award, and he adds: "I couldn't have played any more games than I did and I probably couldn't have played any better than I did at my age.
"I enjoyed being at the club; there were some sensational youngsters who were desperate to learn the game and I'll be looking out for their results.
"Going to Manchester United and winning in the cup was a fairly good day, probably the one big game I remember.
"You have to take the rough with the smooth because you get a lot of knocks in football, but the mark of a man is how you bounce back from them.
"It's a very friendly club and it's disappointing to leave but the bottom line is you take whatever challenge is in front of you and hopefully it is the right option.
"There's no reason why West Ham can't get back up there if everyone gives the manager their full backing."