London Irish came from 17 points behind before losing 27-20 to Grenoble in Pool 5 of the European Rugby Challenge Cup.

The visitors briefly led by three points early in the second half, but a try from Clement Gelin in the final phase of play sparked celebrations in the stands as Grenoble snatched the win.

It took Grenoble just six minutes to make a breakthrough as Gio Aplon sprinted beyond a couple of challenges before offloading to Arnaud Heguy, who stormed over the line for the try which was converted by Gilles Bosch.

The pace of Grenoble's moves quickly saw them pull further clear of the visitors as a patient approach ended with Fabien Alexandre diving over to give Bosch the job of converting a second try.

Irish's response was swift thanks to Johnny Williams, whose power proved to be too much as he charged through a tackle to make the path clear for a try, with Chris Noakes converting.

Bosch hit back with a penalty to make it 17-7, and Grenoble would continue to ask questions of their opponents with long spells in their territory.

However, the momentum shifted before the half-time interval when impressive work by the forwards was followed by Jebb Sinclair sprinting clear for the try, and a conversion from Theo Brophy-Clews reduced the deficit to just three points.

Brophy-Clews added two penalties earlier in the second half to edge the visitors ahead, before Bosch hit back with one of his own to pull Grenoble level.

A defensive showing of the highest class followed from both sides as neither team managed to break the stalemate over the next half hour, but there was a twist in the final minute as Gelin raced clear of his tiring rivals to score the crucial try and Christophe Loustalot added the conversion to bring a dramatic night to an end.