With the teams level after 67 minutes the Argentinian replacement was put clean through by centre Seilala Mapusua and looked certain to be the home side’s hero.

But in what was one of the biggest clangers in league history Leguizamon went for the fancy flying touchdown, took one hand off the ball to start celebrating - and lost control with his other.

As the crowd gasped in disbelief all the South American could do lying on the ground was bury his head in his hands.

If Wasps had gone on to win, which they might easily have done, Leguizamon might not have been able to show his face for a while.

But instead full-back Riki Flutey, who will be with Wasps next season, kicked the winning penalty six minutes from the end.

There was still time for the visitors, seeking to go third in the table, to snatch victory, but their replacement Danny Cipriani failed to find wing Chris Bishay with the line begging two minutes later.

As a result London Irish, still with top four ambitions of their own, avoided a third successive defeat to Wasps this season.

Without five of the England pack against Wales – plus injured Phil Vickery - Wasps struggled to impose themselves, but tackled their hearts out and could easily have come out on top.

The Irish were, of course, lacking Mike Catt and Shane Geraghty, but they held the upper hand for most of the 80 minutes.

The only score of an opening quarter in which the Irish dominated possession was an Everitt penalty after 13 minutes, but the pressure eventually produced more points.

After Lawrence Dallaglio, captain in Vickery’s absence, had dropped the ball in midfield Wasps were forced to defend yet again and wing Topsy Ojo broke the tackle of Mark Van Gisbergen, swivelled and made it into the corner for his seventh try of the campaign.

Geraghty’s stand-off stand-in Barry Everitt, the fourth highest scorer in Premiership history, added a fine conversion before Van Gisbergen made partial amends by reducing the gap to 10-3 with a penalty from 40 metres out.

A double-figure difference could have been restored almost immediately, but Everitt struck the post after Wasps had killed the ball.

The Irish lost Everitt early in the second-half and within a minute were brought back to level terms. Josh Lewsey, playing at centre after being dropped by England, and Van Gisbergen made the initial counter-attack.

When the ball came back Lewsey was involved again before Bishay held off Tagicakibau with ease and darted over.

Van Gisbergen landed the conversion and although a Flutey penalty left Wasps trailing again they had seized the momentum and from right in front Van Gisbergen replied in kind to make it 13-13 after 52 minutes.

Gradually the Irish regained the ascendancy and, with Dallaglio among the players taken off by Wasps, the chance fell to Leguizamon.

He blundered, but Flutey’s kick made him feel considerably better. He still will not be allowed to forget what he did, though – and he might never do it again.