
OK, bugs me not to know the answer to things I've read and should have remembered, so phoned the KC to check :D
Official answer is that litters under query must be DNA tested and can be registered with multiple sires only if puppies are by different fathers ....
So, a litter could be registered as pups 1 & 2 sired by Dog A, pups 3 & 4 sired by Dog B.
But pups 1, 2, 3 & 4 could NOT be registered as sired by Dog A OR Dog B.
Hope that makes sense .....
M.