Rams, second in the table prior to kick-off, had led all the way from the 10th minute of a tense, robust, full-blooded, yellow card ridden, derby battle only to concede the first of the two late tries on 81 minutes while down to 13 with two men in the sin-bin. And, just five minutes later, a triumphant Mackay was waving his arms in sheer delight having touched down under the posts after carving open the considerably weakened Rams defence.
The win saw Bracknell snatch second place in the table by a point from Rams with 11 games left in the New Year to sort out the final standings.
As disappointed skipper Andy Amor said afterwards: “It would have been nice to have gone into Christmas with nine unbeaten games but we are just in mid season and there's a long way to go. We are a point behind Bracknell and the seasons not won or lost in December.
And, he added:- “We showed a lot of heart and courage and we put in a good tackling performance. We just got caught out with a few extra men when they had the overlap and, credit to them, they came back and played some good rugby in the end.”
Rams, playing with the slope towards the clubhouse, started brightly roaring into the home half and, from the opening scrum of the match, referee Callum Howard penalised the Bracknell pack for collapsing and Rams scrum half James Brooks banged over the three pointer.
But, within two minutes the home side were all-square as Rams went offside at a ruck and fly half Liam Prescott made no mistake either with his spot kick.
It certainly spurred Bracknell on especially when they were awarded a second penalty for off-side on 14 minutes and, again, Prescott was bang on target.
At least it galvanised the visitors who bounced straight back to snatch the lead once more following some concerted pressure in the Bracknell 22 and the neat combination of fly half Nigel Gumbleton, centre `AJ' Hopkins in open play plus full back Andy Bryans well-placed chip saw right wing Joe Duffelen racing on to the ball for the touchdown over the Bracknell line and his fourth try of the season.
It also brought out a great wide-angle conversion from Brooks to put his side 10-6 in front after 20 minutes.
And he was at it again, some nine minutes later, when Howard penalised the home side for sealing off the ball and Brooks stroked over the place-kick with ease for a well-deserved, 13-6, lead to take them into the second half.
With Bracknell looking twitchy in defence in the early stages, particularly with some well-placed kicks into space from Rams, it augured well for the visitors especially when lock Taylor picked up a yellow card for a misdemeanor at a ruck.
Brooks certainly needed no encouragement to take the spot kick and land his 20th penalty of the season and put his side 16-6 in front.
Rams then brought on prop Luke Batten and promptly lost the former Bracknell man straight away to a yellow card but, nevertheless, were looking to be well on top only for the tide to start to turn especially when hooker Rory Paxton also landed up in the sin-bin in the 73rd minute.
The reshuffle meant uncontested scrums with replacement Ian Jeffrey on for a second time and as an acting hooker which gave the home side the impetus they needed.
And when Ollie Poole also picked up a very harsh yellow card the writing was on the wall for the visitors.
Some huge Backnell pressure finally told on the 13 man visitors as they wisked the ball wide and Taylor grabbed his try followed swiftly by McKay to touch down the ultimate winner.
Rams did have one last hopeful shot at goal as the seconds counted down but Brooks mammouth 40 metre penalty fell short precipiatating some huge celebrations from the home side when the final whistle sounded.
A fuming head coach and Rams director of rugby Mike Tewkesbury stated aftrewards: “There's still 12 games left to play and what we've got to do, coaches, management and the players, is to go away and learn from that and to scheme and plan and turn things around from that and you do that by two things - brains and hard work!”
Rams: Bryans; Poole, `AJ' Hopkins, Bryant, Duffelen; Gumbleton, Brooks; Weller, Paxton, Baker; Kenneally, Bryson; Owen, Amor (c), Hopkins. Reps – Batten, Jeffreys, Hill.

Report by Steve Williams