For the sake of fairness, I suppose I should note that new information has come to light.
Campus Watch now claim that they cut the chain of a totally different bicycle at approximately the same time as my colleagues bicycle was stolen. Also that they have been in touch with the supposed owner of the bicycle they liberated, asked for a photo of the bicycle they liberated for him, which matches the bicycle they remember liberating, and does not match my colleagues bicycle.
Oh, and all the CCTV cameras in the area – captured nothing!