The British pair beat Vasek Posipsil and Daniel Nestor in a four set marathon, eventually winning 7-6 (7-1) 6-7 (3-7) 7-6 (7-3) 6-3 in three hours and eight minutes.
It means that Britain only need to win one of Sunday’s remaining two singles matches to advance to the quarter-finals of the World Group, after taking a 2-1 lead in a best of five match tie.
Britain’s number one this weekend, Dan Evans, will have the chance to seal the tie when he takes on Pospisil in tomorrow’s opening match. Should it be required, Kyle Edmund will play teenager Denis Shapovalov in a deciding fifth rubber.
Quick court makes it tough for returners
With talisman Andy Murray absent this weekend, Britain were always going to be relying on their doubles duo to give them an advantage going into the final day.
Even so, it was never going to be easy for the British pair, who were facing two doubles specialists on a speedy indoor court in Ottawa.
The experienced Nestor, 44, has won eight Grand Slam doubles titles while Pospisil is a former Wimbledon doubles champion, after winning the title with American Jack Sock in 2014.
Breaks of serves were hard to come by and the first three sets were all decided on tie breaks.
Surprisingly the three breakers were all abrupt and one-sided, with Britain comfortably winning the first and third, while the Canadians ran away with the second.
A single break of serve decided the fourth, as Murray and Inglot recorded their second victory together as a Davis Cup pairing.
Brits save set point before taking the opener
The Brit’s cleared an early hurdle by saving a set point on the Inglot serve at 5-6 in the opening set.
Inglot, who wasn’t broken in the entire match, delivered a crushing serve out wide when the pressure was on, providing Murray with a routine volley.
The British pair carried their momentum into the tie break, which they dominated, winning it by seven points to one.
A lapse in concentration allowed the Canadians to breach the Murray serve at the start of the second set, however it didn’t take long for the Brits to respond.
They targeted the Nestor serve, which looked the most vulnerable early on, and drew level at 4-4 before forcing another tie break.
Murray and Inglot hold their nerve
Once the Canadians had levelled the match, the visitors earned a chance to break the Pospisil serve mid-way through the third set, however Inglot missed a hanging volley on break point.
Suddenly it was the younger Canadian, Pospisil, who looked susceptible on serve, and he doubled faulted on the opening point of the third set breaker before the Brits took a two-sets-to-one lead.
Pospisil, who required treatment on a leg injury in yesterday’s singles match, began to wilt as the match wore on and he lost his serve again in the fourth, following a couple of thrashing returns from Inglot.
The Brits served out the match to 15 a couple of games later, putting their side in the driving seat ahead of the final day.