Greenwood scored the only try of the match when he spun through a tackle by Irish fly-half Barry Everitt to touch down between the posts in the 27th minute and leave Paul Burke an easy conversion and Harlequins celebrating.

The contribution of Greenwood, Burke and full-back Nathan Williams, with three second-half penalties, enabled Harlequins to end their long run of away failure the day before the second anniversary of their last victory on the road – at Rotherham on March 17 2001.

With Newcastle securing a home victory over champions Leicester Tigers, Irish were left bottom of the table facing a grim battle to avoid the drop.

Ironically, it happened on the day when they attracted a club record crowd of 18,585 – more than 4,700 than the previous best in last season’s St Patrick’s Day fixture and the biggest crowd in the Premiership this season – in Reading’s Madejski Stadium.

Irish laid on music, bands and an ample supply of Guinness but the scrappy match failed to mark the occasion.

The desperation of two sides haunted by the fear of relegation was all too evident.

Harlequins surrendered possession at four of their line-outs in the early stages, while the Irish pack was pushed around in the scrums and mauls.

Irish failed to capitalise on their early attacking opportunities with Everitt’s ninth-minute penalty all they had to show for their first-half efforts.

The league’s leading points scorer then squandered an early second-half chance to cut the deficit to a single point when he uncharacteristically missed a simple penalty shot.

Irish sent on newly-capped England prop Mike Worsley to try to shore up their pack in the 45th minute but they never looked like turning the match around.

Quins went further ahead in the 60th minute when, with Burke limping, full-back Williams took over to land his first penalty.

Everitt’s unhappy afternoon ended at the same time when he was replaced by Mike Horak.

Williams, hit the post with his second penalty attempt but made amends by landing his next in the 74th minute and then, after Mark Mapletoft kicked a consolation penalty in the 80th minute, Williams had the final say with his third in injury-time.

And, even though the Guinness flowed as the Irish fans partied on long into the evening in the station car park to celebrate their patron saint, it was simply a case of drowning their sorrows.