Filmmaking / Directing : Help!!! by Louise Camish

A bit random, I have a client who has requested a prop chair, similar to Graham Nortons Big Red Chair, that when you pull a lever the chair falls backwards. The lever and chair don't need to interact, we can fake that, but I need a chair that safely tips backwards with a person in it, that can be controlled from off camera. If anyone has any ideas or knows of a fabricator who can make one, or of a place I can hire one from, please let me know. Needs to be in London, I have 10 days! Thanks :)