Hello sorry for the panicky post but I've just gone to ice a 12 inch vanilla sponge and its all marbled inside with darker patches and I'm not sure whats happened, its the first time I've made a cake this big and the tin leaked so its not gone well so far as it is.
It looks like this -
Is it ok or should I bin it and start again??
If you used vanilla or some darker flavoring, it looks like it was not folded in all the way. It would depend on your recipe. Did you get a chance to trim any cake off? If it tasted fine, it is probably OK.
Probably flavoring not folded completely is my guess.