Northampton saw off London Irish 15-9 at Franklin's Gardens in a result that moves them provisionally five points clear at the Premiership summit.
Ken Pisi's converted try moved Northampton into a 7-0 lead but Shane Geraghty's penalty kept Irish in the contest at the break.
Sam Dickinson then touched down in the second period before a second Geraghty effort off the tee reduced the arrears once more.
Stephen Myler eased Saints' nerves with a three-pointer and, although the Exiles' fly-half kicked his third penalty with 12 minutes to go, the league leaders held on.
Jim Mallinder's men went into this game with 10 wins from 13 matches while Irish had secured just four during the course of the 2014/15 campaign. The odds were therefore stacked in the hosts' favour but, with the Midlands' outfit short of their international players, Brian Smith's side perhaps felt they had an opportunity to upset the applecart.
They certainly started brightly enough, limiting the Saints' clear-cut chances in attack and also having periods of pressure in the opposition 22. But neither team displayed enough quality in the crucial areas and the encounter remained locked at 0-0 after 25 minutes.
However, Northampton were beginning to exert some pressure and they finally opened the scoring through Pisi when a Myler cross-field kick was touched down by the winger.
Irish continued to show plenty of resilience, though, and a Geraghty penalty moved them to within four points. The Exiles' fly-half could have reduced it to one at the interval following yellow cards to Tom Court and Salesi Ma'afu, but his effort drifted wide of the uprights.
Despite a battling display in the first period, Smith's men struggled to build on that early in the second-half as Tom Guest was sin-binned after persistent pressure resulted in a string of infringements. Northampton capitalised as Dickinson crossed the whitewash before another three-pointer from the visiting pivot made it 12-6 in the home side's favour.
Myler and Geraghty then traded penalties as the gap remained at six points. However, with their confidence lifted Irish made one last charge, but the Saints kept them out.
Tries: K Pisi, Dickinson
For London Irish:
Pen: Geraghty 3
Northampton: 15 James Wilson, 14 Ken Pisi, 13 George Pisi, 12 Tom Stephenson, 11 Jamie Elliott, 10 Stephen Myler, 9 Kahn Fotuali'i, 8 Sam Dickinson, 7 Phil Dowson (c), 6 Calum Clark, 5 Christian Day, 4 Samu Manoa, 3 Salesi Ma'afu, 2 Mike Haywood, 1 Alex Waller.
Replacements: 16 Matti Williams, 17 Ethan Waller, 18 Gareth Denman, 19 James Craig, 20 Teimana Harrison, 21 Lee Dickson, 22 Sam Olver, 23 Ahsee Tuala.
London Irish: 15 Andrew Fenby, 14 Topsy Ojo, 13 Fergus Mulchrone, 12 Eamonn Sheridan, 11 Tom Fowlie, 10 Shane Gergahty, 9 Scott Steele, 8 Tom Guest, 7 Conor Gilsenan, 6 Ofisa Treviranus, 5 Jebb Sinclair, 4 George Skivington (c), 3 Halani Aulika, 2 David Paice, 1 Tom Court.
Replacements: 16 Jimmy Stevens, 17 Leo Halavatau, 18 Richard Palframan, 19 Sean Cox, 20 Luke Narraway, 21 Tomás O'Leary, 22 Theo Brophy-Clews, 23 Alex Lewington
Referee: Andrew Small
Assistant Referees: Kelvin Stewart, Ashley Rowden
TMO: Sean Davey