Bit off topic but bear in mind that Lancasters and other heavy aircraft were flown, for the most part successfully, by pilots with very little experience. In NZ we had CPL's flying single pilot in DC3's on agricultural ops for many years, in fact there was one fellow who had approval to ferry them single pilot,when he was holding only a PPL. The ATPL was I believe originally to qualify skippers for international operations. Back in the days when one also had to hold a Flight Navigators licence to go offshore. There was a licence called Senior Commercial for domestic ops, that has now gone the way of the Dodo.
Prospector