As transport networks suffered a second day of disruption, the London assembly announced on Tuesday that it would investigate how prepared the capital was for its worst snow in 18 years.

A whitened Clapham Junction. Experts doubt it would be cost effective to buy special equipment for a once-in-20-years snow storm

However, transport experts query whether it will ever be cost-effective for systems to be readied constantly for events likely to occur only once every 20 years.