Where it says ‘cover with baking paper’ - it means butter the paper well, put a finger width pleat in that cover paper, then add a similarly pleated sheet of tinfoil on top and tie around just under the rim of the pudding basin with string - there’s a reason pudding basins have a substantial rim. It’s a good idea to make a handle by tying the ends of the string together over the top - this greatly eases removing the pudding from the water later without burned fingies. The pleat prevents the pudding from exploding and covering the kitchen with hot golden syrup. Ask me how I know. No don’t. It’s embarrassing. And I had guests over at the time. Set a timer to check for more boiling water every 15 mins - and ONLY add water that’s freshly boiling from the kettle. I like using a stockpot rather than a saucepan - and use a shallow trivet on the bottom under the basin for better water circulation.