An embodiment of the method commences with some initialization steps 10 and 11, which include defining parameters for first and second jackpots. A loop commences at steps 12 and 13 at which current values of the first and second jackpot prize pools are calculated. At step 14 the CPU 2 determines whether storage criterion has been met. If so, the process flow moves to steps 15, 16 and 17. If not, the process flow moves directly to step 18. At step 15 the current value of the second jackpot prize pool is stored as a “pending prize”. Steps 16 and 17 effectively reset the second jackpot. At step 18 the CPU 2 determines whether the award criterion has been met. If not, the process flow loops back to step 12. If so, the first jackpot prize pool is awarded at step 19, along with one or more of any pending jackpot prizes, in accordance with a jackpot prize distribution scheme, then the pending jackpot prizes are deleted. At step 20 the award criterion is redefined and at step 21 the first jackpot prize pool is reset, before the process flow loops back to step 12.