Ben signed a three year deal for an undisclosed fee with Manchester City during the summer 2004. Up until then the Welsh international had played all his football in London, but decided to move on after Leicester was relegated. He admitted that he was excited by the set up at City and was looking forward to bedding into the team next season.
"I was contacted and spoke to Kevin Keegan and decided then to come up here to have a look. Everything was completed within a couple of hours. I was shown round the training facilities at Carrington and they are really terrific. The pitches look great and everything seems to be so well organised. It is just a very impressive set-up. I am really looking forward to it now. Manchester City are a massive club and there was no saying no. Now I just want to get on with it, do my best and hold down a first team place."
Ben played three seasons for Manchester City in which he battled against Stephen Jordan and injuries for the left back position. His no nonsense displays collected applause from the fans, but on 23 August 2006 he took it a bit too far when a mad challenge on Portsmouths Pedro Mendes sent the midfielder crashing into the stands. Mendes required oxygen at pitchside and suffered a seizure while being transferred to hospital but was luckily discharged the next day. Thatcher only received a yellow card by the referee but was suspended by the club and sidelined for 6 games.
For some time Ben had expressed his desire to move to London, and in
January 2007 he made the switch to Charlton Athletic. However his arrival
could not help the club from being relegated.