Christmas puddings, oldfashioned pressure cooker... anyone know how to use them?

[fossil97]

Ok so today is Day of the Puddings.

The instructions are steam for 20 minutes and cook under pressure for 2.5 hours. Now my usual pressure cooker is my mum's old Prestige Ultra which has a valve you turn from steaming to pressure cooking, that's OK.

I have another pressure cooker which I'd like to use to save time (5 puddings) which I don't have instructions for, it's one a bit like this with just the one pressure valve in the middle. Do I take the weight off for steaming and then put it on for pressure cooking? And do you really run it under the tap to release the pressure?

Any help very much appreciated