The Cavaliers scored two tries in the last 10 minutes to snatch the victory, putting an end to the hopes the Bulldogs had of beating the defending champions, especially when they led 32-21 midway through the second half.
Boland made a mound of errors during the match and some of their tackling was more appropriate for those dancers in tutus that former Springbok coach Peter de Villiers was so fond of mentioning.
Border dominated the opening stages to rack up an 18-3 lead, using their backline to great effect as wings Chrislyn van Schalkwyk and Chumani Booi both crossed for tries.
But the Cavaliers managed to claw their way back to just a three-point deficit at the break, through tries to centre Jaquin Jansen and pacy scrumhalf Neil Papier.
The action moved to-and-fro with dazzling speed in the second half, with loose forward Shane Spring opening the scoring for the Bulldogs with his try, converted by fullback Quinton Crocker.
But Jansen was not just a marvellously elusive runner in East London on Saturday, he also added some immaculate goal-kicking to his exploits and his third and fourth penalties kept Boland in touch, even though the Bulldogs ran in their second try of the second half through scrumhalf Lesley-Dean Ruiters.
The Cavaliers had been hard on attack for lengthy periods of the second half, but had been repulsed by impressive Border defence, but the visitors finally found the precision and consistency they had been searching for the whole match in the last 10 minutes.
The whole backline was involved as fullback Eric Zana ran in a superb try and Boland were finally in front when replacement centre Cheswin Williams crossed for the match-winning try in the 72nd minute.
Jansen, who did more than anyone to inspire the victory, then kicked a penalty in the dying moments to seal the win, which was hardly impressive as the Cavaliers played in fits and starts for 70 of the 80 minutes.
For the Bulldogs, scrumhalf Luiters was always in the thick of the action, but it was not enough to continue the hard times the Eastern Cape side are having in this competition.
Border Bulldogs – Tries: Chrislyn van Schalkwyk, Chumani Booi, Shane Spring, Lesley-Dean Luiters, Ruan Jacobs. Conversions: Quinton Crocker (2). Penalty: Crocker.
Regent Boland Cavaliers – Tries: Jaquin Jansen, Neil Papier, Eric Zana, Cheswin Williams. Conversions: Jansen (2). Penalties: Jansen (5).