At the time those photos were taken, the aircraft wouldn't have been too bad. The minimal paintwork is the remains of one of the multi-coloured patches applied to the otherwise natural metal airframe, to aid in formating for the various camera angles required during filming of the BoB movie the previous year. The aircraft had been owned and flown by Jeff Hawkes, who disappeared in a light aircraft, in 'mysterious circumstances', I think in the late '80's. Apparently the Mitchell, lightened by the removal of many uneccessary fittings, handled more like a fighter than a bomber, according to Hawkes.
The hemispherical, optically correct nose cone was made and fitted especially for filming, and a large astrodome-like perspex dome fitted in place of the top turret, together with a retractable camera 'turret' in the belly.
The aircraft was subsequently used for a number of years for other aerial filming work, including, AFAIK, the war movie 'Hannover Street', filmed at Bovingdon, UK (also used for 633 Sqn., The War Lover etc), with a further 6 or more B25's as 'stars'.