Beetroot and potato gratin

This recipe was taken from a Lucas Hollweg autumn special in the Times. He has a great knack of writing articles that make you want to go and cook - straight away.
The ingredients in this dish signal the beginning of autumn - and the flavour is very autumnal and earthy.
Lucas suggests having this with a roast - and we had left overs on their own with some greenery to cut through the creaminess.
The colour is magnificant.

Serves 4 (very well)

500g beetroot
500g floury potatoes, such as King Edward
300ml double cream
200ml whole milk
2 garlic cloves, crushed
6 sprigs thyme
slat and pepper

Preheat oven to 180 / gas mark 4
1. Peel the potatoes and beetroot.
2. Slice with a mandolin, keeping the beetroot and potatoes separate
3. Mix the cream, milk, garlic and the leaves from 4 sprigs of thyme. Season well.
4. Put a thin layer of the mixture in a 23cm gratin dish.
5. Put a layer of potato, followed by a layer of beetroot, seasoning each layer as you go.
6. Finish with a layer of beetroot (keep your neatest slices for the presentation on the top!)
7. Pour the remaining cream mixture over the top, and press down the vegetables with your hands.
8. Lay the remaining thyme on top.
9. Cook for 1 hour
10. Remove from the over and leave to settle for 10-15 minutes.

This really is worth cooking while the shops are full of fresh beetroot - when it's gone it's gone!