Originally Posted by WHBM
The small-bore side tunnels were built for such traffic. One was for pedestrians (in the 1950s presumably quite a few Heathrow workers walked in from buses on the A4) and one for bicycles.
Each of them had a cycleway and a footpath. Wish I had a quid for every time I walked it (before the days of cash dispensers, run out of money on a Saturday night, spend half Sunday trekking out to LHR and back just to cash a cheque).