Put a large pan of salted water on to boil. Finely grate the lime zest into a bowl. Squeeze in the juice. Add 1 tbsp each of the Demerara sugar and Worcester sauce and stir to dissolve the sugar. Add a pinch of chilli flakes (they're spicy, so use as much or as little as you prefer) and a large pinch of salt. Stir again to mix well.
Peel and finely slice the red onion. Add it to the lime and chilli dressing. Stir to mix well and set aside. The dressing will lightly pickle the onion while you make the rest of the salad.
Scrub the Jersey Royals and chop them into bite-size chunks. When the water is boiling, add the potatoes to the pan and simmer for 15-20 mins till they are tender when pierced with a knife.
While the potatoes simmer, halve the avocado and scoop out the stone. Scoop the flesh out of the avocado skin and roughly chop it. Pop it in a large bowl.
Add the lamb's lettuce to the avocado. Drain the potatoes and add them to the bowl too. Pour in the onions and their lime dressing. Gently toss to mix and coat everything in the dressing. Heap the salad up in 2 warm bowls and serve straight away.