Tigers' Michael Obaseki tried to snatch the game with a power move under Worthing's basket. However, Irish's hand covered the ball and forced the Thames Valley forward back to the floor before the hooter sounded to end the game and add the play- off crown to Worthing's First Division title.
Tigers had recovered from 44-34 down at half-time to regain the lead at 56-55 through Nigel Lloyd. As Worthing's supply of chances dried up Thames Valley began to believe they could add the play-off title to their NatWest Trophy.
Lloyd put them 74-70 ahead with over three minutes to play but they never scored again. Cleave Lewis clawed two points back for Worthing, but Irish missed a free-throw to leave the Tigers clinging to a 74-73 lead with two minutes left.
Then Nick Cooke fouled Nelson. Both coaches called successive time-outs and Nelson had to wait almost four minutes before walking to the line to take the shots which won the game, with a helping hand from Irish.
CARLSBERG CHAMPIONSHIP PLAY-OFFS (Wembley Arena): MEN: First Division semi-finals: Worthing Bears 74 Guildford 73; Thames Valley Tigers 97 London Towers 87. Final: Worthing Bears 75 Thames Valley Tigers 74. Second Division final: Crystal Palace 90 Doncaster 87 (Crystal Palace promoted to First Division). Third Division final: Sheffield 81 Leicester 55. WOMEN: First Division final: Sheffield 64 Northampton 63.