London 15th birthday restaurant treat

[StrawberryPi]

My niece is coming to London with her parents for her 15th birthday in a few weeks. We would like to take them out as a treat, probably on a Sunday to breakfast/brunch or afternoon tea although lunch is an option too - we want to fit in around some sight-seeing.

We don't see her very often so I'm not too sure of her tastes. We want somewhere a bit special, not too worried about price, and in terms of areas we're pretty much talking anywhere central. Would be great to hear of anywhere that has been a hit with the 15 year olds in your lives!

Thanks everyone! Definite food for thought here... turns out my tastes are different to the average 15yo, who'da thunk it!?

Any more suggestions will be gratefully received!

It's been an interesting thread as it's given me suggestions for my 16 yo DD. I will say though, we've recently returned from London and as a treat I took her to some nice restaurants (The Ivy etc) as a treat which she was really up for but then the pressure of having to dress and behave accordingly put me on edge which put her on edge and it wasn't the most relaxing time I thought it would be. She enjoyed it but in her words, I prefer something less formal and more relaxed.