I don't think I've ever made a Christmas cake where it didn't curdle a bit on adding the eggs. If you had added the rest of the flour with spices and whizzed it a bit, it would have been fine. Yes, it is the "proper way" to whisk the eggs first and then add them a teeny bit at a time, but I, like Grannynorm, lose patience and finish up tipping it all in. You can't tell the difference in the finished product, not in a cake that is more fruit than actual cake. Hope you didn't throw away all that lovely egg and butter!