1. First make the lemon butter. Dice the butter and put it in a mixing bowl, add the lemon juice and zest and plenty of pepper. Mash it together with a fork, then beat with a wooden spoon until well incorporated. Scoop out on to a sheet of clingfilm and roll up to form a sausage shape. Chill in the fridge for at least 1 hour.
2. Use a potato peeler to remove any coarse skin from the asparagus but leave on the top 5cm/2in including the head. Trim off the woody white part from the bottom.
3. Preheat the grill until nice and hot. Brush the asparagus with olive oil and lay the asparagus on the grill rack. Turn the asparagus every 2 minutes until nicely browned and cooked through, which takes approximately 8 minutes.
4. Cut the lemon butter into 12 even-sized slices. Lay the asparagus out on to warmed serving plates, season with Maldon salt and pop the lemon butter on top. Tuck in straight away.