I added a gallery with photos of Air Defence variant of Chieftain (with Marksman turret - it is armed with two Oerlikon guns, just like German Gepard). The tank is a new exhibit in Duxford Imperial War Museum - all photos were taken by Mark Bentley of IWM and published with his permission.
I think this moster is interesting subject for scratchbuilders - all that is needed is Tamiya Chieftan hull + Tamiya Gepard gun pods + some scratchbuilding
http://vodnik.net/index_gal.htm (scroll down the page to find link to Chieftain gallery)

Best Regards,
Pawel