Market Harborough arrived at Belgrave to find rain and sleet had left the pitch far from ideal for their style of running rugby.
And things got worse when their try-scoring machine Ed Parker was injured in the warm-up.
They did, however, start the game well and after Joe Whitworth put in a stunning clearance kick to within 30 metres of the Belgrave line they were on the attack.
The lineout ball was scrappy from Belgrave and Josh Purnell pounced on the ball and drove forward.
Quick recycling and powerful running by Jack Digby created good ball that went wide and a slick move by Harris Medwell released Harvey Slade to run through and touch down for a 5-0 lead.
But Belgrave are a tough side to beat at home and the conditions suited them as they use their power to create territory and by half-time they had kicked three penalties for a 9-5 lead.
Harborough again started strongly in the second half with Purnell and Adam Blatchly combining well.
A kick ahead led to another score as Laurence Joel followed up to tackle the receiver and when he lost hold of the ball, Medwell was on hand to pick up and touch down.
But Harborough were having an uncharacteristically bad afternoon in the back line as they were constantly caught in possession and rarely was the ball passed without a knock-on.
They were perhaps justified in believing that Belgrave were closing them down too quickly from an offside position but that does not excuse the lack of discipline or scrappy performance.
The Harborough forwards did not back down and the defence was once again solid with Timmy Waterfield once again leading the tackle count preventing Belgrave from scoring a try.
They did, however, have an excellent kicker and his two further successful kicks saw Belgrave run out victors by 15-10.
Director of rugby David Nance said: “We need to put this performance behind us.
“In many ways it changes very little as, to gain promotion, we have to beat the teams that are in the battle.
“The positive thing is the growing strength in depth of the club with three senior teams playing in addition to the Colts.
“And the third team, a mixture of Vets and young players, secured a 19-5 victory at Oadby Wyggs.”