Yep, it's a Dijon mustard vinaigrette, the baby spuds are roasted, and the wild rocket is just wild rocket.
Well it got me drooling and there's no way I could describe my current state as hungry. I reckon I'd cycle London to Leicester for a plate of that!
Talking of vinaigrette, I remember eating a traditional Corrèze dish, tête de veau, at a street festival in Ussel. I gagged on the bits of calf head - you chew and chew and it keeps springing back into its original shape, you try to swallow but the bits expand in the throat and plug it up. But the sauce was, in effect, a hot vinaigrette, and delicious to boot. I've been eating warm mixed salads (heat from rice or pasta, etc) in vinaigrette ever since. Think of them as winter salads.