My Whirlpool ADP962 won't start?

My elderly 962 (17 years old) will not start. The various lights on the control panel light up as the programme switch is turned and the rinse-aid light is on (we use all-in-one tabs) but pressing the start button has no effect. Neither does holding it down to end the programme.

The machine obviously did not finish the cycle last time around as there was still water in the base, but I have bailed it out and cleaned all the filters, to no effect. Any thoughts?