Defender Seth Nana Ofori-Twumasi has made his loan move at Northampton permanent after agreeing a two-year contract.
The former Chelsea trainee made 11 appearances for the Cobblers this season whilst on loan from Peterborough.
Town manager Gary Johnson told the official club website: "As our supporters would have seen from his loan spell, Nana can play as a right-back or cover in midfield.
"He has got power and pace and we have agreed to bring him in on a permanent deal having seen him improve each game when he was with us on loan.
"Not only did he perform well for us, he went through the pain barrier for the sake of the club when he was on loan, putting himself out there when we needed him when other players would have cried off with injury.
"He is just the sort of character you need in the dressing room."