Tries in both halves helped secure the Exiles a 19-0 win on a ground where they will be hard to beat this season.
Lacking five of the forwards – two of whom have since left the club - who were on duty in the play-off final second-leg win at Bristol back in May didn’t help the Doncaster cause.
But Knights boss Clive Griffiths, who looks to have recruited well, will be pleased that his side lasted the pace well and twice came close to a late consolation try.
He will, however, look to improve on other aspects of the club’s display ahead of Saturday’s home game against Rotherham.
Irish posted the first points of the game, fly-half Tommy Bell, a close season signing from Leicester Tigers, kicking the first of three penalties in the first quarter to secure his side a 9-0 lead.
Knights went close to a try on 33 minutes after successive penalties had enabled fly-half Declan Cusack to pin Irish in the corner.
Half-back partner Michael Heaney went blind after a driving maul had been halted only to see debutant hooker Harry Allen lose the ball in the ball in the tackle just short of the line.
Unfortunately for Knights, it only proved to be a stay of execution as fellow centre Tom Fowlie touched down for the first try on the stroke of half-time after good work by Irish following a catch and drive to make it 14-0.
Knights made a spirited start to the second and would have pegged three points back on 46 minutes had Dougie Flockhart hit the target with a penalty attempt.
But Tikoirotuma touched down for a close-range try to seal the visitors fate 10 minutes later.
*London Irish: Tonks; Neal, Fowlie, Williams, Tikoirotuma; Bell, McKibbin; Hobbs-Awoyemi, Paice, Franks, Robson, De Chaves, Narraway, Cowan,Treviranus. Replacements: Ellis, Court, Hoskins, Sexton, Trayfoot, Allinson, Ransom.
*Doncaster Knights: Jarvis; Flockhart, Hayes, Clark, Lewis; Cusack, Heaney; List, Allen, John, Challinor, Nolan,Young, Robinson, Shaw: Replacements: Nelson, Hislop, Sproston, Makaafi, Owen, Humberstone, Edgerley