Preston Walker of World Service tells us what works and what doesn’t in his restaurant

Slow Roast Belly Pork with a Rosti Potato and Brambly Apple Sauce. This dish is very popular. We came up with it four years ago but it's quite a classic because the flavours go so well. Belly pork is quite a trendy meat at the moment, people enjoy the taste and enjoy the fact that they are experimenting with different cuts of meat.

It is also great from a restaurant's point of view because it's a cheaper cut of meat.

It probably costs us about a pound per portion and we sell it for £16.75.

Grilled Kidneys. We do this now and then as a special. The kidneys are cooked in the suet, which keeps them moist, and then served with roasted vegetables and red wine sauce. They're just not popular enough to put on the menu full-time.

Kidneys are quite an acquired taste; some people who ate kidneys as children find it hard to get their heads around eating them now, as maybe they weren't cooked properly or the quality of the ingredient wasn't great. They're not a terrible seller but I think the sign of a good menu is when you are selling evenly across the board, and this one lagged behind.

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