However, not for the first time on a balmy evening, Munster showed tremendous resilience and it was stand-in captain Paul Warwick who settled the nerves with a superb long range penalty in the 78th minute.
Speaking after his side's second pre-season success in Cork, coach Tony McGahan expressed his satisfaction with the performance.
"Yes, very happy with that. Tonight was a step up and a great result," he said.
"The young lads were tremendous again tonight. Our defence was good. We mixed in a few of the older boys and good to have them back too.
"But the squad have been working well and that work has shown. So all in all very happy with the performance."
London Irish quickly ate into the Munster lead after the break with try from Sailosi Tagicakibau converted by Lamb who had earlier added a penalty.
But then the Musgrave Park faithful were treated to a superb try when Ireland Under-20 speedster Danny Barnes scored on the right after superb hands from Tom Gleeson and replacement Scott Deasy.
Warwick converted but a Jamie Leonard drop goal and Lamb's conversion of Stowers try set up a nervy finish.
But it was Munster - reinforced by second half replacements Mick O'Driscoll, Peter Stringer, Denis Fogarty and Felix Jones - who held their nerve best to emerge as worthy winners of the Jack Wakefield Memorial Trophy.
It was the second successive year that these sides competed for the trophy which honours the memory of the three-year-old London Irish supporter Jack Wakefield whose inspirational battle against a brain tumour touched the hearts of people across the world.
MUNSTER: Denis Hurley; Danny Riordan, Tom Gleeson, Paul Warwick (capt), Danny Barnes; Jeremy Manning, Toby Morland; Dave Ryan, Damien Varley, Tony Buckley, Ian Nagle, Billy Holland, Tommy O'Donnell, Niall Ronan, Denis Leamy.
Replacements used: Felix Jones for Hurley, Scott Deasy for Manning, Peter Stringer for Morland, Julien Brugnaut for Ryan, Denis Fogarty for Varley, Mick O'Driscoll for Leamy (all half-time), Dave Ryan for Buckley (59 mins).