Brynric: I checked the cache today and it was in fact there, but so was a load of unpleasant rubbish. The area has suffered from thoughtless drivers in the past and it isn't the pleasant picnic spot it once was. There is an excellent series passing close by and so I think its time for Conspirators Crossing to be honourably retired. Many thanks to all the finders.
As for the clue which seemed to cause some folk such difficulty (chocolate teapot indeed), I thought it was suitably criptic. The find was a small container magnetised to the iron work at the east end of the bridge.