London Wasps romped to four-try bonus point victory over London Welsh, Tom Varndell clinching the final score to win 34-15 in Oxford.
Joe Simpson had an outstanding game as Wasps came from behind with tries from wing Elliot Daly, replacement prop Will Taylor and, right at the end, a fourth try for wing Tom Varndell.
Welsh fly-half Gordon Ross kicked all his side's points with five penalties, while Wasps fly-half Nicky Robinson landed three penalties, Daly booted one and replacement stand-off Stephen Jones kicked the only conversion of the match.
Wasps were looking for to repeat their win over the Exiles at Adams Park, Wycombe, back in October.
Welsh, meanwhile, needed to bounce back from a 13-6 loss at Worcester.
Although not in any immediate danger at the wrong end of the table after basement side Sale Sharks beat Worcester on Friday night, revenge on their near neighbours would be welcome for head coach Lyn Jones if only to steer them further away from the dogfight below them.
The first half-hour was dominated by the boot, both with positional kicks and shots at goal, as first Welsh took a six-point advantage and then saw it clawed back by their visitors.
There was not a great deal to choose between them up front but the most obvious mistake made by the field kickers, Welsh full-back Tom Arscott a particular offender - was booting the ball straight into touch and losing the territory that would have gained.
Wasps could have led handsomely at the interval had they taken the majority of their goal kicks. Daly missed a long-range effort for the visitors before an excellent scrum from the Exiles and an offside decision given their way saw Ross secure two successes.
But the lead did not last long as ex-Wales international Robinson levelled matters with two penalties but then sent two more penalties wide of the uprights from similar distances of 25 metres.
Ross, on the other hand, was deadly accurate at that short range. As Welsh frustrated their opponents and the front row of Franck Montanella, Neil Briggs and James Tideswell caused havoc for opponents Zak Taulafo, Rhys Thomas and Phil Swainston, Ross secured another two goals to take his side into a 12-6 interval lead.
But, even though the ball may have been greasy from the earlier rain, there was little excuse for a poor first-half with hardly any invention in attack towards either try-line.
Robinson reduced the arrears after the break to three points with his third penalty before a piece of individual magic took the match up a gear.
In what will surely be one of the contenders for try of the season, Simpson took the ball from a line-out thirty metres from the Welsh line, went through a gap at the back and embarked on a diagonal sprint across the pitch.
He looked to be going nowhere but somehow found a gap towards the line. The scrum-half ran through three tackles and got past desperate defence on the line to touch down and leave everyone in the crowd amazed.
Robinson failed with the conversion but that put Wasps two points to the good and, when Daly kicked a thumping penalty from fully 53 metres, it was the turning point of the contest.
Wasps were on top and they threatened to leave Welsh with nothing to show for their efforts when Daly sprinted down the right wing to just get in for the second try of the game.
Welsh would not lay down, and Ross' fifth penalty put them within sight of Wasps. But a final killer converted try from replacement Will Taylor saw Wasps home and dry.
Vardnell went over on 83 minutes to get the bonus point and put Wasps challenging for a top four place on Saturday.
For London Welsh:
Pens: Ross 5
For London Wasps:
Try: Simpson, Daly, Taylor, Varndell
Pens: Robinson 3, Daly
London Welsh: 15 Tom Arscott, 14 Dan Caprice, 13 Seb Jewell, 12 Sonny Parker, 11 Nick Scott, 10 Gordon Ross, 9 Rob Lewis, 8 Alfie To'oala, 7 Mike Denbee, 6 Ed Jackson, 5 Kirill Kulemin, 4 Jonathan Mills (c), 3 James Tideswell, 2 Neil Briggs, 1 Frank Montanella.
Replacements: 16 Greg Evans, 17 Tom Bristow, 18 Greg Bateman, 19 Matt Corker, 20 Adam Balding, 21 Nick Runciman, 22 Alex Davies, 23. J Lewis.
London Wasps: 15 Hugo Southwell (c), 14 Elliot Daly, 13 Andrea Masi, 12 Chris Bell, 11 Tom Varndell, 10 Nick Robinson, 9 Joe Simpson, 8 Billy Vunipola, 7 Jonathan Poff, 6 Ashley Johnson, 5 James Cannon, 4 Joe Launchbury, 3 Phil Swainston, 2 T Rhys Thomas, 1 Zak Taulafo.
Replacements: 16 Tom Lindsay, 17 Tim Payne, 18 Will Taylor, 19 Marco Wentzel, 20 Sam Jones, 21 Charlie Davies, 22 Stephen Jones, 23 Chris Mayor.