I understand that not only is there more sunlight in sub-Saharan Africa than there is in this country but also that they have a higher amount of the UVB wavelength than we have here.  This would appear to be the basis of the provision of a lamp or tube to compensate reptile species such as the leopard tortoise when they are kept in our country.
Alas, when researching this subject I find that this is where the science ends and speculation begins.  There appears to be no clear consensus as to how much UVB a tortoise actually receives from a lamp, how many hours per day the lamp should be on, if it would get any benefit from being on at night, if there are other aspects of husbandry which produce the same effect or how one would know when the lamp needs to be replaced.
I would be grateful if anyone could tell me a source of generic data on this subject (and by that I mean anyone who does not have a commercial interest in the matter).
Yes, I am aware that it was an act of irresponsibility to sell my wife and I a leopard totoise when we were 62 and 67 years of age and when neither of us had any real knowledge of reptiles or any idea that it was the 4th (now the 3rd) largest specie of tortoise.  However our Rocky is now 9 years old and not doing too badly at the moment.

Hello John,