1 - Put a deep roasting tin onto the bottom shelf of the oven, and make sure that there’s another shelf directly above it.

2 - Pull the roasting tin out on its shelf, fill two-thirds with boiling water from the kettle, then carefully slide it back in.

3 - Heat oven to 180C/160C fan/gas 4.

4 - Tear off a large sheet of foil and greaseproof paper (about 30 x 40cm).

5 - Sit the greaseproof on top of the foil and butter it.