London Irish (20) 34
Tries: Homer, Mapusua, Seveali'i, D Armitage Cons: Malone 3, Lamb Pens: Malone 2
Brive (6) 13
Try: Namy Con: Orquera Pens: Orquera 2
Mapusua scored the second try for the Exiles on Saturday
London Irish beat Brive to stay top of Heineken Cup Pool Six with a last-gasp Delon Armitage try earning what might prove to be a vital bonus point.
A converted Tom Homer try put the Exiles in front, before Luciano Orquera landed two penalties for the visitors.
But converted Seilala Mapusua and Elvis Seveali'i tries, and two Chris Malone penalties, gave Irish total control.
Brive crossed through Guillaume Namy late on before Armitage clinched a four-try bonus point at the death.
The bonus point ensures they remain top of their pool ahead of Leinster, who also have 15 points from four games after securing a bonus-point win over the Scarlets.
It was a memorable return to action for Armitage, who came on as a 66th-minute replacement for his first action since injuring his shoulder three months ago and rapidly laid down a marker for England ahead of the Six Nations.
The full-back could have marked his return with a try soon after taking the field but was taken out near the line by Scott Spedding, who became the fourth Brive player to be sin-binned.
Armitage was not to be denied though and showed superb pace to race over under the posts with the final play of the game.
London Irish head coach Toby Booth:
"You joke about it being fate but you saw Delon Armitage's true class. When you give him the ball, that is what happens.
"He has been excellent for the last two weeks in training. He was fit to start but the plan is to drip-feed him back in.
"I was a bit disappointed we hadn't achieved it before then but I wasn't that anxious because we were creating opportunity after opportunity and we were probably a bit greedy in how we wanted to get it.
"It was more about just being patient and waiting for the gilt-edged opportunity. It couldn't have come any later."
London Irish: Hewat; Homer, Seveali'i, Mapusua, Rudd; Malone, Lalanne; Dermody, Paice, Ion, Kennedy, Casey, Thorpe, S Armitage, Hala'ufia.
Replacements: Lennard for Seveali'i (69), D Armitage for Rudd (66), Lamb for Malone (63), Murphy for Ion (52), Coetzee for Casey (60), Roche for S Armitage (63), Stowers for Hala'ufia (52).
Not Used: Rautenbach.
Brive: Jeanjean; Cooke, Noon, MacKay, Namy; Orquera, Pejoine; Kinchagishvili, Thompson, Zimmermann, Uys, Browne, Forgues, Azoulai, Domingo.
Replacements: Spedding for Jeanjean (56), Perry for Pejoine (41), Henn for Kinchagishvili (41), Barnard for Zimmermann (12), Dubarry for Browne (63), Idieder for Domingo (54).
Not Used: Claassen, Agulla.
Sin Bin: Barnard (50), Noon (52), Spedding (71).
Ref: James Jones (WRFU).