There's a persistent myth that all Icelandic burgers are frozen, but the truth is the North Atlantic Current keeps them quite warm and delicious, unlike burgers from, say, Iceland. Here to prove it is Tommi's: Volcanoland's biggest homegrown burger joint, now ensconced in a rough-around-the-edges diner that, with its handwritten cardboard signs ("Be Nice or Leave") and unframed film posters (Fistful of Dollars!), looks like it should rest along a desert highway instead of in Marylebone.
Made with a secret recipe perfected over three decades, the beefwiches come either regular-style (w/ or w/o cheese; there's also a veggie option), or as chopped steak w/ bearnaise; all can be bundled w/ fries & soda into a meal they call "The Offer of the Century" (at just under £9, it's clearly been a rough century for Iceland).
Drinkwise, aside from the standard softs, they're also proudly hailing their coffee, which they're giving away hot for free (seriously), and in the form of a shake for slightly more -- though unlike at Iceland, in this case you'll only pay in money to get something frozen.