The cake is designed to take on the classic look of a pint of Guinness, with its rich dark brown bottom and fluffy white top. But it contains Guinness too - and that is what gives it its beautifully moist texture. Don't worry though, it doesn't taste of beer.
One of the best recipes I've found is this one by Nigella Lawson, laden with butter, sugar and topped with a vanilla cream cheese topping. It's certainly not for the faint hearted, but then this is a celebration cake, so I think its ok to push the boat out every once in a while!
And if you don't fancy making your own and happen to be visiting Brighton, I can't recommend Ground highly enough.
All photography © Heather Elizabeth Wilkinson 2013