The narrow success against a below-par Quins was just reward for the visitors as John Kingston’s men were left to regret losing three men to yellow cards at different points throughout the game.

Forwards Fraser McKenzie and Allan Dell scored in either half and with James Chisholm, Kyle Sinckler and Dave Ward spending time in the bin, Edinburgh deserved to come out on top.

Mathew Luamanu and Joe Gray grabbed two late consolations for Quins to ensure they salvaged a losing bonus point, but Duncan Hodge’s men are now a point clear at the summit with only Timisoara Saracens left to play.

Their victory also saw them win at the venue where they lost the 2015 Challenge Cup final to Gloucester Rugby and secure a double over the Quins.

It was visitors Edinburgh who turned around 13-6 ahead, McKenzie’s try proving the difference between the sides.

Scottish fly-half Duncan Weir exchanged early penalties with Harlequins No 10 Tim Swiel before McKenzie came up with the first try of the day. The second row hit a lovely line to break clear and cruise over the line with the home defence barely able to lay a hand on him.

Weir converted and booted another penalty after Mike Brown was pinged for holding on and with Quins forward Chisholm shown a yellow card for a professional foul on the half hour mark, the home side were up against it.

Edinburgh lost Scottish international prop WP Nel to a head injury assessment before the break, but boss Hodge would have been happy with his team’s work.

Swiel responded with a second home penalty and saw another monster kick at goal from the halfway line fall short to leave his team needing to come from behind in the second half.

Quins weren’t helped by losing Sinckler to another yellow card just minutes after the restart, the England man getting a 10-minute rest for striking Magnus Bradbury while being held back.

That proved to be a crucial moment as just minutes after the prop departed, Edinburgh moved further ahead.

From inside their own half numerous phases saw Hodge’s men produce a free-flowing attacking move which ended in the most unlikely of scorers.

Prop Dell was the man to finish it off beneath the posts and with Weir adding the simple extras, Edinburgh were now 14 points clear.

The hour mark saw both teams make a raft of replacements, with Sam Hidalgo-Clyne among the new faces coming on to the field for Edinburgh.

But Quins’ bench failed to make an impact and Ward then became the third home player to see yellow for a professional foul.

Weir kicked the resulting penalty and although Luamanu and Gray helped Wasps score 12 points in the final three minutes, Quins were left to pay the penalty for their ill-discipline as Edinburgh moved into the box seat for a quarter-final spot.