One of London’s little gems is the Grant Museum of Zoology in the University College London campus just off Gower Street. There is a fantastic collection of specimens here from all over the world, correlated together in a neat ball (and sometimes with a darkly humour *jar or moles,below)
Although I kind of prefer the Natural History Museum in Dublin, due to the genuine feeling that it has been locked in a time capsule since the late 19th century and the heyday of zoology, there are definitely more specimens (and in a much better condition) here.
If you are a fan of Damien Hurst you can see many of his themes here such as animals in formaldehyde (granted it isn’t a shark but a bunny head cut in two and laid in formaldehyde is definitely an interesting sight to see.)
Also, this museum is completely free and rarely busy which is a rarity in somewhere like London where most tourist sights are jam packed and expensive.
So, highly recommended, a must see (though possibly not for the more squeamish)