Mapletoft – missing last week through injury – made a triumphant return to the action, bringing some deft touches to the midfield as well as his top-notch goal-kicking skills.
Fittingly, given his tremendous influence all afternoon, the former England international had the last word of the afternoon, going over for a try on the stroke of full-time to apply the coup de grace to Leeds.
The pivot had opened the scoring in this high-scoring match, kicking his first points in the 2nd minute as the Exiles took the initiative against a Tykes side who were very slow out of the blocks.
Mapletoft was again to the fore some moments later when he cut through the first line of defence to give a scoring pass to team-mate Kieron Dawson for the opening try.
He added the conversion and then kicked two further penalties in the first half to put his side well ahead by the break – despite a late rally by Leeds.
Leeds did actually come with three points of the Exiles in the second half after they created a try for Duncan Hodge, but the rest of the half saw Irish fully in control, winger Paul Sackey scoring his side's second try.
With Mapletoft on song, London Irish were able to ride out the rest of the half in comfort, Leeds never threatening to overhaul their opponents.
For London IrishTries: Dawson, Mapletoft, SackeyCons: Mapletoft 2Pens: Mapletoft 4
For Leeds Tykes:Tries: HodgeCons: HodgePens: Hodge 3