Ampthill survived a second half Caldy revival to claim victory in their first ever visit to Paton Field.
A’s began by conceding on three minutes when the first of a number of missed tackles from both sides resulted in a converted try under the posts.
The response came on 13 minutes when a 5m scrum was driven over the line for blind-side flanker Matthew Burke to touch down, converted by fly-half Joseph Tarrant.
Burke was playing at number 8 due to the visitors being a man down after a yellow card to Maama Molitika.
Just six minutes later and restored to a full complement, a trademark lineout catch and drive saw openside flanker Joseph Bercis over the line for his 29th try of the season. Tarrant failed to add the extras.
There was a marked contrast in styles, with Caldy rarely retaining possession for more than three or so phases on attack but looking dangerous with ball in hand, while Ampthill were more patient.
On 23 minutes Amps were penalised at a ruck 40m out but the penalty goal was struck sweetly and successfully by the home side’s centre.
A’s pack drove on for the next 10 minutes, but it was a break from centre Brendan Burke which saw him draw the last man and release William Goodge to touch down, with Tarrant converting for a 19-10 lead at half-time.
There was no further score until the 52nd minute when Burke evaded four tacklers inside the Caldy 22 to crash over to the right of the posts, converted by Tarrant.
From the restart Molitika broke the line on halfway, drew the cover and delivered the scoring pass to scrum-half Gavin Williams – again, Tarrant adding the extras.
Now trailing by 33-10 many teams might have let their heads drop, but Caldy’s response was dynamic.
First their replacement hooker touched down for an unconverted try on 62 minutes, followed just two minutes later by a converted try out of defence by their centre.
On 74 minutes their right wing danced through multiple defenders for a converted try, but Ampthill’s experience eventually told as Tarrant increased the gap to seven points to wrap up the win.
Caldy tries: Banks (3), Jones (62), Roberts (64), Eaves (74)
Conversions: Roberts (3, 64, 74)
Penalty: Roberts (23)
Ampthill tries: Burke M (13), Bercis (19), Goodge (32), Burke B (53), Williams (58)
Conversions: Tarrant (13, 32, 53, 58)
Penalty: Tarrant (76)
Half Time: 10-19
Referee: Michael Harris