Kevin, a former apprentice at Upton Park, had to go to Swindon to get first team football before moving to Manchester City, but he has always had the Hammers at heart, and he says: "It was strange walking back to Chadwell Heath but I am over the moon and my family is too.
"It was always a dream of mine to play for West Ham but I never got the opportunity first time around so I am made up.
"I was sad for a while to leave but looking back it was probably the right decision because I went to Swindon, got my first team opportunity there, and learned a lot from that.
"I got experience in the Premiership and learned from Glenn Hoddle - and met the missus along the way as well!
"Probably, looking back, it was the right choice and I ended up getting a great move to Manchester City, which I loved.
"I was there for seven years and it was a big part of my life, but, as soon as Kevin Keegan told me that I had a chance to come back to West Ham, I was straight in the car.
"I always used to come over and watch the games with my mates and doing YTS here was a big enough thrill - but to get the chance to come back now and hopefully do well is fantastic.
"I am sure I have still got a lot to offer; I feel great, as fit as I ever have done, and I think it is the right time to leave Manchester City and come back to West Ham.
"All I can assure them is I will be doing my best - I will give 110% and hopefully that is enough to win the fans over.
"But the main thing is to be winning games; I want to come here and if I can help a little bit towards getting us back to the Premiership I will be happy.
"My immediate family, my mum and dad, have been following my career and going up and down the motorway to watch City over the last seven years.
"But they are as thrilled as me that I am coming back to West Ham - as is my wife because I always said I would love the opportunity to go back there and play.
"We were talking to each other in the hotel last night and it is strange how it has all happened."
He will be looking to play alongside another Hammers fan, Rob Lee, in the midfield; he, too, expected to have put on a claret and blue shirt long before this summer, and Kevin reckons a team full of West Ham fans might just do the trick.
"That wouldn't be a bad thing; we need to dig in and work hard," he says.
"The talent I have seen in training is as good if not better than at City so I am sure we have got a great chance.
"I have only been out there for one session but I have certainly seen enough; I have always looked at West Ham's results and the way things are going - and to go down with the points total we did was disappointing as it is.
"But I think the lads have got what it takes to be capable of bouncing straight back - looking at the quality, it is comparable with City and I am really looking forward to it.
"I haven't really had the chance to speak to many of the lads because I have been training, rushing around, and getting things sorted out.
"But I am sure I will get to know them soon and playing my part in what I hope will be a good season."
In the modern era, of course, transfers take days, weeks, or even months of negotiations - with Kevin it was signed and sealed within 24 hours of Kevin getting to know about Glenn Roeder's interest.
"It was yesterday that I heard about the move; we had a UEFA cup game against the Welsh side TNS and basically I reported, was getting on the coach to go to the hotel for food and a rest, and the manager has called me up to the office," says Kevin.
"I didn't have a clue what was going on, to be fair, I just sat down and he said 'West Ham.'
"That was it, and I thought 'you don't need to ask me twice'; I took it in a little bit and said 'of course I would.'
"I was in the car, obviously getting home to tell the wife, and she understood fully what I wanted to do without me even saying anything to her.
"I just had to say that West Ham were interested and she knew that I would want to come down and sign; luckily enough I have been able to do that and now I am just looking forward to working with Glenn, his staff, and the rest of the lads.
"I am sad to leave City, I couldn't say otherwise; I have a lot of good friends there and it is a great club with a lot of support.
"There will always be fondness for the club but this opportunity was too good, way too big - an offer that I had to take even though it results in having to move the family."
Having suffered relegation in his career, Kevin knows that the fallout is often disastrous, and explains:
"It can be; I have been relegated before with teams and players have left, but it brings the nucleus of the lads that are left even closer together.
"I haven't seen anything to suggest otherwise here; it is a great bunch of lads together, joking, and, more importantly, they have go the quality.
"But I never ever doubted that, as I know most of them anyway by following West Ham."
And so, instead of looking to face Charlton - and Paolo Di Canio - in the Premiership opener on Sunday, he is now hoping to face Sheffield United on Saturday.
"It has been a bit of a rush, I will have to admit that," he says.
"I was in the hospital having scans and medicals at half past two in the morning, which isn't ideal, but I think I will just get through this weekend, if selected, on adrenaline alone.
"Hopefully I won't let anyone down, and now word gets out that I have signed I am sure the calls will come in for tickets, so I'll have to turn my phone off!"
Has anything changed since he was last here?
"Not a lot, suprisingly; there is the odd building here and there that has been added on but the actual nucleus of it is the same and it is nice to see a few familiar faces in Tony Carr, Jimmy Frith, Shirley the cook still knocking about, and the kit man Eddie.
"It is really strange walking in but it won't probably sink in until this afternoon when I am resting up - then it will probably hit home that I am back."
Kevin told me last season that he would still love to play for the Hammers one day, and he recalls:
"I sort of said that tongue in cheek, really - it was a dream that I thought would never happen, and with me signing a new contract at City last year I thought perhaps I would be playing my days out there.
"But this has come along, it has obviously surprised me, but delighted me at the same time - it is a dream become reality so I am just looking forward at getting started now."
As for his preferred role, he adds:
"I think centre midfield is probably my favourite position but as a footballer you want to be involved and it is up to the manager where you play or even if you play.
"I am not coming here thinking I am guaranteed a starting place; I am going to come here and have to work as hard as at Manchester City.
"It is a strong squad with a lot of midfielders and a lot of young lads coming through as well, so I will have to knuckle down and earn the right to get the shirt on as well.
"It is up to me what I do with it then, if I keep hold of it or let it go, and I am looking forward to the challenge."
If West Ham hadn't come along it is probable that Kevin would have remained where he was, and he says:
"I would probably have stayed at City; we were really settled up there, I had been there seven years, the kids were in school, and we had good friends up there.
"I had two years left on my contract and had just moved into a new house - but this was an opportunity that I couldn't let pass by, it all went up in the air and I have to start again."
Kevin, who has 32 Northern Ireland caps, doesn't have to worry about whether dropping a division will affect his international career.
"I packed in international football; we have got three children, my wife is pregnant, and it was just all getting a bit too much travelling away," he says.
"First and foremost I didn't want to risk getting injured, the kids were getting older and starting to miss me, and I just felt it was the right time to do it.
"So I called it a day, even though I had had great times playing for Northern Ireland and enjoyed every minute of it.
"But I hope they appreciate and respect my decision, and I am sure they do because I did give everything for them."
The move will allow him to resume his acquaintance with Northern Ireland skipper Steve Lomas, and Kevin adds:
"Obviously Steve is a quality player, he has proved that over the years, and I am sure when he is fit he will be straight back in there - and nothing but an asset for us."
As for his physical condition, he adds:
"I am fit, though I have not played as many games as I would have like over preseason - but that is obviously Kevin Keegan's selection.
"But I am quite fit anyway and hopefully if selected I won't look too unfit; I will just give it my best shot and see how it goes."
He hopes to face Sheffield United at the weekend, and adds:
"It is going to be a difficult game and I am fully aware that West Ham have had a good start to the season with two wins in two games out of two potential banana skins.
"Preston is a difficult place to go and it was Rushden's cup final on Wednesday.
"It gets more difficult when you drop out of the Premiership because everyone looks at you as a big scalp - I had it exactly the same at City, they raise their game 10 or 15%.
"That makes it very difficult - but from what I have seen on show we have got plenty to cope with that." And the key to getting out of the first division?
"The main thing is the ability, which I have seen, and the other major thing I noticed when we got out of it at City was togetherness."
And Kevin says, that even though he needed no time to think about the move to the club he loves, he went south with an endorsement of Glenn Roeder ringing in his ears.
"I have seen everything I needed to with my own eyes and Glenn didn't have to sell it to me.
"I have had been worded up from Arthur Cox, Kevin Keegan's assistant, and he said 'you couldn't be going down to work with a better man'.
"I respect Arthur and Kevin a lot and for them to say that made me think it was the right decision to make."
Kevin played 211 league and cup games for the City, scoring 42 goals.