Grant, a summer signing from Lincoln City, claimed his first goal for the club with a classy finish early in the second-half. He revelled throughout in an advanced midfield role and won the penalty from which Jonson Clarke-Harris made it 2-0 in the first-half.
Posh, who also had the boost of a goal in the first minute, moved up a place to 22nd after breaking a four-game losing streak. Birmingham had been unbeaten in three away games before Posh trimmed them up.
“It was important to get a win after two difficult performances,” Grant stated. “We have been good at home so far and we played some great football at times and deserved the win. We wanted a fast start, but we didn’t expect one quite that quick.
“We mixed it up well. We passed out from the back when we could and we played it up to Jonno (Clarke-Harris) early when we had to.
“When they had a high line we played past them and when they dropped deeper we had space to play in midfield. It really was a good performance.
“It was great to get a goal. Siriki Dembele is such a good player he draws players towards him so I just found some space and waited for the pass. It was also good to have a hand in Jonno’s goal. I ran behind the defence from just inside their half and I didn’t want to shoot too early, but then the ball got stuck under my feet. I saw the defender coming though and made sure I stayed between him and the ball and it was a clear foul.
“We were really good in the first-half. We could have been better in the final third at times towards the end, especially me, so there’s even improvement to come.”