If you are watching the american president on the telly delivering a speech
in Westminster Hall take a look if you can at the roof. It is one of the
great medieval roofs, a carved oak hammerbeam structure spanning 70ft.

It's suprisingly difficult to find a good picture of it for you. If I find
one I will post it, but the Hammerbeam structure is used where no single
timber is long enough to span the roof, and there are no intermediate
arcades and columns. It was designed and constructed without engineering and
calculation, but by the craft tradition, experience and experiment.

Tim w