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From James Sandemans

I enjoyed Paul Collins’s article on metal balloons down the ages (10 January, p 44). I am not sure, however, about his remark that, since 1941, “no more metal-clads have taken to the skies”.

I seem to recall reading, 30 or 40 years ago, of a successful project at the Massachusetts Institute of Technology to design, build and fly a balloon constructed entirely of lead.

The editor writes:

• MIT’s neighbours at the consultancy flew both a lead balloon and a dirigible in May 1977: see photos at . The US TV programme Mythbusters also managed to loft a balloon made of lead foil in January 2008.

Glasgow, UK