Biggar, without 12 injured players, sustained their first Tennent’s National Division 1 loss since going down at Highland in September 2019.
“We weren’t at our best,” Biggar secretary Mike Booth told the Carluke and Lanark Gazette. " I don’t think we had the speed at the back that we normally have and we certainly weren’t dominant in the scrum when we’ve been very strong there this season.
"I have to say Heriot’s were very strong opponents for some reason. We didn’t expect them to be with their position in the league.
"I think the boys were a bit deflated after losing but they pick themselves up, they always do.
"They don’t let their heads down, they just get on with the job and usually that pays off. I think we just needed another five minutes and we’d have got the job done.”
After going behind to an early unconverted try, Biggar hit back to lead 7-5 when Rowan Stewart romped home from 40m and Andy Jardine did the needful with his boot.
After Biggar’s Craig Borthwick was yellow carded, there was then controversy as referee Tom French appeared to miss the ball being dropped before being touched down by Heriot’s and Callum Anderson’s try was given before converted by Graham Wilson and the hosts were 12-7 up.
Two Jardine penalties put Biggar 13-12 up at half-time, before his third penalty increased the lead to four points.
But Heriot’s then established a 24-16 advantage thanks to tries by Jacob Lineen – son of ex-Scotland international Sean - and Lewis Govenlock, the latter being converted.
A Borthwick try converted by Jardine made it 24-23 but the hosts scored a try to go six points up with less than five minutes left.
Rowan Stewart’s second try brought Biggar to within a point but Jardine’s tough conversion attempt from the touchline went wide.
Second placed Biggar, one point behind Gala after seven games, host Highland in the league this Saturday, KO 3pm.