I applied to UCL for Anthropology and was offered AAB. Yesterday my results were actually ABB (socio, RS and english lit) and they still gave me the place.
I'm going ahead and assuming its because Anthropology is possibly* an under-subscribed course in comparison to subjects like Law and engineering.
The fact that they accepted me goes to show they can be quite lenient but I believe it truly depends on your course and how close you were to the offer. I hope it went well for you!