Place the chopped veg on the bottom of a decent sized roasting tin.
If you have a trivet, place it over the vegetables and put the beef on top. If you don't have one, you can just place the beef joint on top of the veg.
Season the beef well with sea salt and freshly ground black pepper and give it a massage!
Pour 500ml of water into the tin to cover the veg (this will make your gravy so don't let it evaporate in the oven).
Cook for the desired time (see the table above) at 180°C/gas mark 6.
At the end of cooking time, check the joint with a meat thermometer (see the table above) and if it's ok, remove it from the oven to rest.
In the meantime, scoop out the veg from the liquid, then pour the stock into a fat separator.
Pour the stock out of the separator into a bowl, leaving any fat behind.
Add the cooked veg to the stock and add 2 stock cubes.
Blitz in a food processor until smooth. If it's too thick, add a little more water and a few drops of gravy browning if you're using it.
Stir well and serve. Or, you could let it cool and either freeze it or keep in the fridge until you're ready to use it.