The lanc flew with 2 trained pilots.... where do you get single pilot from, or do you mean single seat ?
actually bomber for the most part it was a single pilot, at the start of the war there, technically, was a co-pilot but he was later renamed as the Flight Engineer, however the flight engineer could almost always fly the aircraft comfortably for several hundred miles back to base and there are infact stories of the flight engineer actually landing the craft, although with not as much grace as the proper pilot

it'd have to be pretty bad by that stage however as there are just as many stories of pilots landing the craft with just one hand, she was a very forgiving aircraft to fly as all her pilots will testify.......
that being said it wasn't unheard of for a second proper pilot to be carried, infact it was standard proceedure, newly trained pilots would fly a few missions with an experienced crew as a "second dickie", so there will always be someone around that can fly the bird.........
Next point bomber is very correct in saying it was possible to fit a second set of controls if nessisairy, as has been done with today's flying lancs, obviously it wasn't considdered very important to the RAF, and this's what i can make of why........
the Pilot was the most expensive crew member to train, putting two in every bomber would cost twice as much as putting one in every bomber. The next bit of logic is that there will
always be some attacks that even a second pilot can't save you from, such as your fuel blowing up and ripping the aircraft to shreads, so you've lost two pilots in one go and there was no point in having the other pilot. The RAF figured they'd put this extra pilot in annother aircraft, that way they can, for the same money as having a co-pilot, put an extra 14,000lbs on target, furthermore if the one plane has that attack that no co-pilot can save you from, you've only lost one pilot not two, because the other one's miles away in a completely different plane! slightly morbid thinking perhaps, but in a way it makes sence, experience with the twin pilot stirling made them think there's not many situations where a co-pilot can save you, and they occour so rarely that it's not worth the extra expence.........
now on to the issue of daytime bombing, this was covered last time we we argued the case of the lanc and B-24, and i calculated that in a daytime bombing career of over 40,000 daylight missions the lanc carried out, she suffered an average loss rate of only 0.7%, which for over 40,000 sorties isn't bad!