Bennett eventually did a U-turn and signed for Peterborough United on 23 October 2009 on an initial three-month loan deal with a view to a permanent move.
Grimsby chairman John Fenty had a change of heart, and following a slow start to the season for his club, he decided to cash in on the Town skipper literally only days after sacking manager Mike Newell.
Posh manager Darren Ferguson said of the transfer: "Ryan is an excellent signing for us, he has potential and fits in with our policy of bringing good, young players to the football club".
Bennett made his loan at London Road permanent on 23 January 2010, signing a four-and-a-half-year contract, with Grimsby reportedly receiving £500,000, possibly rising to £1 million.

Bennett scored against Barnsley on 3 December but Barnsley won 4–3.
Bennett's final game for Peterborough was away at Doncaster, the Posh were 1–0 down in stoppage time until Bennett went down the wing and hooked the ball into the area for Tyrone Barnett who headed in on his debut after coming off the bench.
Bennett eventually did a U-turn and signed for Peterborough United on 23 October 2009 on an initial three-month loan deal with a view to a permanent move. Grimsby chairman John Fenty had a change of heart, and following a slow start to the season for his club, he decided to cash in on the Town skipper literally only days after sacking manager Mike Newell. Posh manager Darren Ferguson said of the transfer: "Ryan is an excellent signing for us, he has potential and fits in with our policy of bringing good, young players to the football club". Bennett made his loan at London Road permanent on 23 January 2010, signing a four-and-a-half-year contract, with Grimsby reportedly receiving £500,000, possibly rising to £1 million.
Bennett scored against Barnsley on 3 December but Barnsley won 4–3. Bennett's final game for Peterborough was away at Doncaster, the Posh were 1–0 down in stoppage time until Bennett went down the wing and hooked the ball into the area for Tyrone Barnett who headed in on his debut after coming off the bench.
Ryan Bennett (footballer)