Known as the British Steam Car Challenge, the project is in California right now and is likely to break the record any day now. That means going over 145mph while powered by hot water (heated by propane).
The vehicle specs are amazing. The Inspire, as it is called, stretches 25 feet in length, weighs 3 tons, and has a steam turbine that generates 360 hp. Theoretical top speed of the car is 170mph. Now that might not sound very fast. There are several production sports cars capable of exceeding 200 mph with internal combustion engines. But an IC engine is inherently dirtier than a steam engine, which can be fired by much cleaner fuels. The problem with developing a fast steam powered car is size. It is possible to build steam engines that generate 3,000 hp but they are huge. Indeed, the only place you are likely to find them is in steam locomotives.
The fastest British steam locomotive, arguably the fastest ever (argued in immense detail here) was the Mallard. It was rated around 3,000 hp and at times it achieved speeds in excess of 120 mph. But it weighed over 100 tons! The Inspire is one eighth of the power with one thirtieth of the weight! That is an amazing feat of engineering.