Despite scoring three tries in six second-half minutes Coventry left Dillingham Park with only a try bonus point to show for their efforts.
Jordon Poole, Ryan Hutler and Jimmy Martin were the quickfire try-scorers for the visitors who as a result led 20-19 at the hour mark.
But the home side’s bench then turned the tide in the fourth quarter and late scores from forwards Samson Adejimi and Nathan Michelow were enough to tilt the scales in their favour.
Playing with the wind, Cov had earlier dominated an opening 40 minutes that was almost entirely played in Ampthill territory.
But after Louis James put them in front, a frustrating sequence of errors kept the hosts in the game before Olly Hartley and Toby Elliot took full advantage of defensive mistakes to give the Mob an unlikely half-time lead.
Cov made the best possible start when Pat Pellegrini’s midfield break and neat offload sent James racing over for a score which the Tongan no.10 upgraded.
Referee Andy Wigley quickly lost patience with the home side’s desperate defence and sent lock Kaden Pearce-Paul to the sinbin.
But despite camping in the home 22, Cov were unable to take advantage of their temporary numerical superiority in conditions which made expansive rugby difficult.
Lucas Titherington went closest to claiming a second score for the visitors when he got over the line but was held in goal.
It was therefore against the run of play when centre Hartley hacked ahead and recovered the ball to go under the Cov posts for a try which Gwyn Parks converted.
And worse followed from a blue-and-white perspective as Elliot charged down James’ attempted clearance and followed up to touch down the hosts’ second score.
Parks’ conversion left Ampthill with a 14-7 interval advantage which they increased by a further six points soon after the restart through his pair of well-struck penalties.
But when the hosts lost prop Luke Green to a yellow card Cov seized their opportunity in style and hit their opponents with a trio of scores.
Newly-arrived replacement hooker Poole scored the first of these from a lineout maul and after Pellegrini converted Cov went straight back upfield and Hutler grabbed his eighth touchdown of the season with a fine chip-and-chase finish.
Incredibly, the visitors had the lead minutes later as their best move of the match ended with the outstanding Matt Kvesic throwing a long pass to Martin who finished acrobatically.
Ampthill’s replacements made an immediate impact on the game and it took a brave intervention from Martin to prevent Charlie Bracken from providing a quick response.
But the hosts now had their tails up and when they forced a five-metre scrum Michelow drove over from close range.
Manu Vunipola converted and the on-loan Saracen split the uprights again two minutes from time after home hooker Adejimi applied the finishing touch to a series of pick-and-drives.
Tries: Morris (31), Elliot (37), Michelow (67), Adejimi (79)
Cons: Parks (31) (34) Vunipola (67) (79)
Pens: Parks (45) (47)
Tries: James (3), Poole (55), Hutler (57), Martin (61)
Cons: Pellegrini (3) (55)
Ampthill: Bacon; Elliot, Morris, Hartley, Harmes; Parks, Bracken; Flynn, Adejimi, Green; Rees, Pearce-Paul; Stonham, Moore-Aiono, Strong.
Replacements: Cutting, Crean, Hardman, Michelow, Smart, Green, Vunipola, Jackson
Coventry Rugby: James; Hutler, Wand, Titherington, Martin; Pellegrini, Chudley; Cordwell, Ma’asi, Nicol; Anstey, Smith; Nkowcha, Ball, Kvesic.
Replacements: Poole, Chilvers, Salt, Bartlett, Owen, Lane, Mitchell, Wilson
Referee: Andy Wigley