Leaking fruitcake

Hi Lindsey
Just made Delia's classic Christmas cake as I have done for the last few years. Only this time I decided to make a square cake as suggested in the recipe . It would appear Delia does not include an 18cm square tin in her range so I went to a well known
bakeware store and bought one there. It has a loose bottom but seemed sturdy enough. I double lined the tin as usual but when I went to look at the cake after 4 hours it would seem that some kind of liquid or butter had poured out of the cake all over the bottom of my oven!! I have never had this trouble before using a loose bottomed round tin.
Did I do something wrong and will the cake be ok?
Perhaps I need a more solid tin?
look forward to hearing from you
Julie