Legs in peril

SIR – In 1940, during the Blitz, there was a sudden and unexplained increase in the number of people in London suffering from deep vein thrombosis.

It was soon established that the vast majority of sufferers had spent the night in an Underground station as shelter from the bombs, often taking a deckchair (Letters, August 8) with them to sleep in.

As the back of their knees rested against the wooden bar across the front of the deck chair, the popliteal vein, which lies behind the knee, was compressed for several hours, causing a clot to form. Simon Pike

Hoarwithy, Herefordshire