Andy Peaks named an unchanged starting XI following the 2-2 draw at Redditch United, although young Oxford United loanee Matt Berry-Hargreaves returned from injury to take a place on the bench.
There were chances at both ends early on with Ben Diamond sending a header across the face of goal for Diamonds while former Hayden Road man Nabil Shariff nodded over from six yards for St Neots.
Despite half-chances for both sides, it was Diamonds who went in front five minutes before the break.
Albie Hopkins had a header hacked off the line from a corner but the ball was played back in and Lorraine brilliantly flicked home from close-range.
And Diamonds were given a further boost just a minute later when St Neots’ Tom Wood was given a straight red card for a studs-up lunge on Ben Farrell, who had to be withdrawn at half-time with Jack Westbrook replacing him.
Diamonds went close to doubling their lead six minutes into the second half when Declan Rogers saw his free-kick rebound off the crossbar before Sam Brown headed wide of the far post following a corner.
Dylan Williams shot over for St Neots but Diamonds grabbed the crucial second on 69 minutes.
Rogers headed goalwards from a Nathan Hicks cross, it was blocked and the ball ran perfectly for Lorraine to fire home from close-range.
Diamonds had the ball in the net again four minutes later but Brown’s downward header from a Rogers free-kick was ruled out for a push.
It didn’t matter, however, as they comfortably saw things out to maintain their good form and move back into the top five in the Evo-Stik League South Premier Division Central.
Diamonds will be hoping to make it seven matches without defeat when they host Biggleswade Town on Saturday.