I saw a Ti Brompton yesterday on the train back from That London, and its owner let me pick it up to feel the weight. I was quite impressed. This was an L-type in old money, with mudguards, but it felt lighter than my part-titanium Brompton with no mudguards and titanium seatpost, which is already only about 21.5lb.
The tubes are clearly oversized and they've done something with the stem clamp too - it has chunky ribs on either side.