No idea why it's done it but i love it and would like them all to do it, i think it's gorgeous !

I have seen this twice before, always with purple ones. It is a mutation that makes several flowers merge into one larger one. I think it looks nice though.

Agree with Kildermorie - its a form of proliferation, nothing to worry about unless the plant starts doing it all over and every year - and these are biennial, so not a problem at all.

What a weird flower. We have a large wildish garden with thousands of foxgloves, but I've never seen one like this. Amazing!

Sue has "achieved" this three years running, as Kildermorie says with the purple ones. I put a pic up yesterday. And as in this case, they are the first ones to open.

There is a certain variety that does this fairly consistently....Aha! Found it! It's 'Monstrosa'.