Despite some wasted opportunity in the first half even playing with a two-men advantage, the 2011 champions scored three tries in the second half to overtake Harlequins and go four points clear.
For London Welsh, regardless of their RFU hearing on Tuesday, their seventh consecutive Premiership defeat puts them firmly in the relegation battle with a tough run of game in the next three rounds.
They showed great spirit and opportunism in the first half to stay in the game but their discipline – over ten penalties conceded in their own half – cost them dearly in the second half and took the game away from them.
Saracens went in front on the first play of the game when Tyson Keats’ clearance kick was charged down and the scrum-half then conceded a penalty trying to regather the ball.
Charlie Hodgson was successful and the home side was 3-0 up.
They enjoyed most of the possession from then on and Hodgson double the lead after 17 minutes with another penalty.
But against the run of play it was London Welsh who scored the first try of the game with their first meaningful incursion in Saracens’ half.
As Saracens were on the attack, the Exiles secured a turnover and counter attacked on the right flank through Tom Arscott.
A couple of phases later, the ball made his way to the left wing to see Seb Stegmann, who only joined the club last Monday, beat three defenders to score.
But Saracens went back on the attack and, after another penalty conceded in their 22, Phil McKenzie was sent to the bin for the visitors.
It didn’t seem to halt the Exiles poor discipline though and, five minutes later, Sarries were awarded a penalty try as a well-worked catch and drive was collapsed by Tom Bristow.
The lossehead was sent to the bin in the process and the home side was now leading 13-5
Despite being down to 13 men, London Welsh scored next as Gavin Henson kicked a penalty but Hodgson replied in kind.
The Welsh fly-half wasn’t done though as, on the last play of the half, he kicked a drop goal to trail only by five points at the break.
Saracens’ inability to score when in the opposition 22 must have been addressed at the break and Joel Tomkins went over following a burst through the middle by Duncan Taylor eight minutes from the restart.
But Welsh were enjoying some possession and from a good attack lead by the forwards, Henson reduced the gap with his second penalty of the game.
Will Fraser, who was once again outstanding at openside, was next on the scoresheet when the Saxons flanker scored in the corner following good hand from right to left from Saracens.
Hodgson couldn’t convert but the score was now 28-14 for the home side.
But it didnt damper the Exiles’ spirit who went back on the attack but were denied twice by the Television Match Official.
First replacement hooker was held up over the line before it looked like Henson scored but TMO Andrew Small ruled Tom Arscott was guilty of crossing in the lead up.
James Short was also denied a try for going into touch just before putting the ball down but Saracens eventually secured the try bonus-point eight minutes from time when the in-form David Strettle went over the line for his fifth try in as many games.
Tries: penalty, Tomkins, Fraser, Strettle
Conversions: Hodgson 3
Penalties: Hodgson 3
For London Welsh
Penalties: Henson 2
Drop goal: Henson
Sin bins: McKenzie, Bristow
Saracens: Wyles; Short, Tomkins, Taylor, Strettle; Hodgson, Wigglesworth; Gill, Brits, Stevens; Borthwick (Capt.), Kruis; Wray, Fraser, Joubert.
Replacements: George, Auterac, Du Plessis, Botha, Saull, De Kock, Mordt, Ransom.
London Welsh: Arscott; MacKenzie, Parker, Jewell, Stegmann; Henson, Keats; Bristow, Bateman, Tideswell; Mills (Capt.), Kulemin; Cabello-Farias, Hills, To’oala.
Replacements: George, Moss, Ion, Corker, Browne, Davies, Ross, Voyce.
Referee: Luke Pearce
Star man: Will Fraser – Saracens
You can relive all the action from the Allianz Park here.