I didn't realise passing under the Clyde had such an affect, that's quite interesting. I would have thought, however, that being mixed overground/underground (o

I didn't realise passing under the Clyde had such an affect, that's quite interesting. I would have thought, however, that being mixed overground/underground (on many London lines) would make air circulation an easier problem to tackle. Ah, I do have similar memories of my (possibly rose tinted) glasses steaming up, but it was always so much cooler and I never felt that I couldn't catch a breath of clean air.