Alex Lewington's hat-trick and Shane Geraghty's brace allowed London Irish to cruise past London Welsh 50-12.
Irish scored six first-half tries to power to a 38-7 lead at the break, before slowing down in the second half.
Neither side headed into the game in strong form, with the hosts still searching for their first Premiership win, and Irish having lost their last four games in all competitions.
This had been earmarked as a potential opportunity for Welsh to end their barren run, but any hopes of an upset were quickly extinguished.
Lewington grabbed his first try after just three minutes when he linked up with Tom Fowlie, and then Fowlie added the visitors' second moments later.
Shane Geraghty missed both conversions but he struck four before the interval as Irish established a formidable lead through further first-half tries from Matt Parr, Andrew Fenby and a brace from Geraghty.
Welsh's only response came on 12 minutes when James Tincknell slid through for William Robinson to convert.
Lewington added a second try on 46 minutes following good work from Tom Guest, which Chris Noakes converted.
Taione Vea helped stem the tide for the hosts with their second try, but the Exiles had the final say in the closing stages.
And fittingly it was Lewington who converted his hat-trick to bring up 50 points for his side after Jebb Sinclair had gone close for the hosts.
Noakes was wide with the conversion, but it counted for little on a satisfying afternoon for Irish, who secure a bonus point to move even further clear of bottom spot and ensure the misery continues for London Welsh.
For London Welsh:
Tries: Tincknell, Vea
For London Irish:
Tries: Lewington 3, Fowlie, Geraghty 2, Parr, Fenby
Cons: Geraghty 4, Noakes
Yellow Card: Fenby
London Welsh: 15 Elliot Kear, 14 Seb Stegmann, 13 James Lewis, 12 James Tincknell, 11 Nick Scott, 10 Will Robinson, 9 Rob Lewis, 8 Opeti Fonua, 7 Carl Kirwan, 6 Ben Pienaar, 5 Matt Corker (c), 4 Dean Schofield, 3 Jack Gilding, 2 Rob Elloway, 1 Eddie Aholelei.
Replacements: 16 Nathan Morris, 17 Nathan Trevett, 18 Taione Vea, 19 James Down, 20 Richard Thorpe, 21 Alex Davies, 22 Olly Barkley, 23 Nic Reynolds.
London Irish: 15 Andrew Fenby, 14 Alex Lewington, 13 Tom Fowlie, 12 Eamonn Sheridan, 11 James Short, 10 Shane Geraghty, 9 Scott Steele, 8 Tom Guest, 7 Conor Gilsenan, 6 Ofisa Treviranus, 5 Nic Rouse, 4 George Skivington (c), 3 Leo Halavatau, 2 David Paice, 1 Matt Parr.
Replacements: 16 Jimmy Stevens, 17 Tom Court, 18 Richard Palframan, 19 Jebb Sinclair, 20 Luke Narraway, 21 Darren Allinson, 22 Chris Noakes, 23 Eoin Griffin.
Date: Saturday, February 28
Venue: Kassam Stadium
Kick-off: 14:30 GMT
Referee: Matt Carley
Assistant referees: Ross Campbell, Jonathan Healy
TMO: David Sainsbury