D'Arcy unscathed but Lions lose
Leinster 12 Ospreys 16
The Neath-Swansea Ospreys moved 12 points clear at the top of the Celtic League, holding off a late Leinster surge for a hard-fought win at Donnybrook.
Ireland centre Gordon D'Arcy had his first outing in four weeks but could do little as a 66th-minute Jason Spice try and the boot of both Shaun Connor and his replacement Matthew Jones helped Lyn
Jones' men to only their third win in nine trips across the Irish sea.
Leinster pilled on the pressure late on and got in for their second try through captain Shane Jennings after Christian Warner's first-half effort had left them 5-3 up at the break.
D'Arcy - who injured a hamstring injury in Ireland's 28-17 RBS Six Nations win over Italy last month - played an hour and sparked the Leinster backline into action late in the first half.
The home side endured a fretful opening as the elusive Spice had a fifth-minute try ruled out for a foot in touch and outhalf Connor kicked just one of three penalty shots. His seventh-minute slot from 40 metres was the game's only score until first-half injury-time.
A Guy Easterby hack-through created havoc in the Welsh defence and with Kieran Lewis drawing his man in, centre Warner had enough pace to outdo Richard Pugh for the corner, and his third try in two matches.
Holwell dinked the conversion wide and was made to pay after 57 minutes as Connor - having missed his fourth attempt early in the second half - made amends for a 6-5 lead.
The Ospreys were beginning to dominate and a blindside snipe nine minutes later saw the Leinster defence at sea. With Dave Tiueti and captain Barry Williams picking-and-driving to good effect, Spice got the touchdown from a close-in ruck.
Youngster Jones tagged on the conversion and added an easy 73rd-minute penalty.
A searing Warner break allowed Jennings set up a grandstand finish but Holwell's touchline conversion mattered little in the end as the Ospreys held on for their 13th and most crucial win of the campaign.
Keith Gleeson continued his return from injury by coming off the bench with 20 minutes to play.