One of our most regular summer barbecue main courses is a butterflied leg of lamb, marinated in thyme, rosemary, lemon and chilli plus – but here’s the issue that we’ll get on to – garlic. Of all the barbecue dishes we do, this probably counts as my favourite, perhaps because of its simplicity. I loosely follow Rick Stein’s method from his first Food Heroes book.

I particularly like doing this dish when we have visitors. It’s easy and I usually let the lamb rest for 30 minutes or so in the oven on its very lowest setting, leaving time to deal with other courses and stay on top of the sides. In fact, I have been known to brave the elements and do this throughout the year whenever the lamb is good, which, given the rolling seasons for British lamb, can pretty much be any time.

We buy most of our meat from The Butchery at Bermondsey Spa Terminus, but there were a couple of occasions earlier this summer when I needed to shop when The Butchery was closed. Inspired by a Borough Market blog posting about Rhug Estate, I decided to give their Borough Market stall a try. Rhug is an organic estate in Denbighshire that I knew had a good reputation among chefs – you sometimes see ‘Rhug’ referenced on menus.

It turned out that Rhug’s salt marsh lamb was at the very beginning of its season. There were two consequences. First, the leg was smaller and so when butterflied required less cooking; it was also a consistent thickness (this was, of course, down to the skill of the butcher – it would have looked more like a vandalised skateboard ramp if I’d had a go…).

Second, the butcher at Rhug issued some very specific advice: when salt marsh lamb is that new, don’t use garlic. I was glad of the advice, but didn’t know how much difference it would make. Don’t you always use use garlic in a lamb marinade? Needless to say, he was spot-on.

My treatment of the lamb, using Rick Stein’s marinade as a guide is pretty conventional, although I tend to increase the qualities of some of the marinade ingredients: a chopped red chilli, a tablespoon or so each of copped rosemary and thyme, the zest of most of a lemon plus the juice of about half, a couple of chopped bay leaves, a teaspoon of salt, some pepper and about 6 tablespoons of olive oil. I mix all the marinade ingredients together, turn the lamb in the marinade and let it sit in the fridge for three or four hours. When it’s time to barbecue, I grill the lamb over a medium flame for anywhere between eight and fourteen minutes on each side: it depends on the thickness –  I like to get it to just pink. While cooking I continue to baste with the marinade. With older lamb, it’s best to cut away some of the excess fat from the flesh side beforehand, although even what’s left can cause big flare-ups

Most recipes would also include garlic in the marinade; Rick Stein suggests two cloves. But twice now, using the new season’s salt marsh lamb from Rhug and following the butcher’s advice, I have omitted it

We have eaten this dish so often that the absence of the garlic was instantly noticeable: it was almost as though there was a perfectly-sized gap that allowed the salty and sweet, juicy flavours of the young lamb to take the podium position. The lamb was beautiful, but more delicate than we are used to, and it was that delicacy that would have been crowded out by the garlic.

Last weekend, we barbecued with the leg of an older lamb – it may have been a Dorset Down – from The Butchery. This was meat that seemed to require garlic, which was the right call. It was a truly fine piece of lamb, with a wonderful juicy texture, but it was denser, with more fat and far more robust flavours. in this case, the garlic seemed to accentuate those other flavours .

From now on, I will be cautious about garlic with the youngest of lamb – I don’t think it’s only about salt marsh lamb, although that will usually be the most tender and succulent.

This has also made me think about why we use garlic. I tend to use it because a recipe says so and I follow the same habits when there is no recipe. I suppose it’s obvious, but I can now see more clearly the way it will overpower delicate flavours but accentuate more robust ones.

I can also now thoroughly recommend Rhug at Borough Market (they also do online sales through their website). Our default place for meat will always be The Butchery, which is consistently outstanding, has a great range, including cuts that we might not otherwise find (who knew you could get a steak from a cow’s rectum? A spider steak, if you think it sounds appealing…) and Nathan and his team never let us down. But I will not hesitate to use Rhug as well.

[Incidentally, this is a dish that responds well to various different sides and you can use the other dishes to emphasise the seasonal nature of lamb. During this summer, we have served it variously with new potatoes and mint, sautéed potatoes with rosemary and garlic, broad beans and peas with onions, braised little gems, courgette fritters and warm red onion and rocket salad]