London - Saracens stayed on course for a domestic and European 'double' after beating London rivals Harlequins 31-17 in the English Premiership semi-finals on Saturday.
Victory at their Allianz Park ground in northwest London put Saracens into a Twickenham final against Northampton, 21-20 winners over arch East Midlands rivals and defending champions Leicester on Friday, at Twickenham on May 31.
Saracens could go into the domestic showpiece clash as the champions of Europe if they win their first European Cup final, against French title-holders Toulon, at Cardiff's Millennium Stadium a week on Saturday (May 24).
But Saracens, who finished top of the regular season standings, were made to fight hard by a Quins side who forced their way into the play-offs with a late charge.
Indeed the visitors, led 17-11 at half-time after Sarries were briefly down to 13 men.
However, second-half tries from Scotland's Kelly Brown and the England duo of Brad Barritt and Chris Ashton turned the match in Saracens' favour while Red Rose fly-half Owen Farrell kicked 16 points.
There was a worrying moment for England coach Stuart Lancaster when Harlequins' full-back Mike Brown, his first-choice No 15, limped off with a suspected hamstring injury in the second half that raised doubts about his fitness for the upcoming tour of New Zealand.
Losing Brown would be a further problem for Lancaster, who already knows he will be unable to select players from Northampton and Saracens for the first Test against the world champion All Blacks in Auckland on June 7 because of the proximity of the Premiership final.
Brown and wing Ugo Monye scored both of Quins' tries, with former All Blacks stand-off Nick Evans adding a penalty and two conversions.
Saracens, down to 13 men for a time after Argentina centre Marcelo Bosch and ex-England prop Matt Stevens were sin-binned in quick succession, found themselves 17-11 behind at the break.
But with former England captain turned club skipper Steve Borthwick playing his last home match before retirement, Saracens recovered to score 20 unanswered points in the second half to advance into the Premiership final three years after they won the domestic title.
Evans and Farrell exchanged early penalties before a second Farrell goal-kick edged the hosts in front.
But Sarries were down to 13 men after Bosch and Stevens were yellow-carded within four minutes of each other.
Bosch was sin-binned by Test referee Wayne Barnes for a dangerous tackle on Evans and Stevens followed for a deliberate knock-on.
A combination of hot sun and Saracens' artificial pitch made for stamina-sapping conditions and Quins made their numerical advantage count to set up a try for England wing Monye, with Evans landing the conversion.
However, 13-man Saracens hit back when a fine handling move stretched Quins' defence and created a try for Scotland flanker Brown.
Nevertheless, Quins led at the break when, after they forced a turnover, England captain Chris Robshaw's kick downfield was regathered by Brown for an opportunist try.
Evans's conversion gave the visitors a useful interval lead, one that looked all the better as Farrell and Bosch missed goal-kicks -- Saracens' squandering a possible 14 points in all.
Weak Quins defence though helped Saracens regain the lead, powerful centre Barritt forcing his way through a couple of initial tackle to score a try by the posts.
Bosch had a 'try' ruled out for offside but Saracens put the result beyond doubt when England wing Ashton, trademark dive and all, crossed for a 62nd minute try.