I recently told a one of my many 'bosses' (I'm a Prison Officer, so I spoke to the governor in charge of the psychologists) She was great, she said that prior to me talking to her, I had passed all the exams and interviews fairly, and few people would guess at a glance about my condition anyway, (I'm frequently refered to as just weird and eccentric). I am currently in an admin/management role where I pretty much am left alone anyway.
I would suggest writing a paper letter explaning the condition, highlighting any positive aspects, showing that it is your approach to the work that is different, not the the quality/efficiency of your work. Give it to your boss to read it, and be prepeared to discuss it later. Have you had any contact with the National Autistic Society, as you're in London? They are good for advice, support and advocacy.
Good luck
_________________
mostly harmless