Many leading bike builders in the UK during the 1930s, 40s and 50s preferred to use their tubesets as th were air hardening, which become stronger when brazed, unlike the maganese based Reynolds tube which is weakened by heating.
Many leading bike builders in the UK during the 1930s, 40s and 50s preferred to use A&P as it was air hardening, unlike the maganese based Reynolds product which was not. Air-hardening tubesets actually become stronger when brazed, unlike the normal steel tubing sets, such as 531, which are weakened by heating.