To mark the 75th anniversary of the foundation of the Guide Dogs for the Blind Association, BBC Disability Affairs Correspondent Peter White examines the changing role of the working dog, from the early 1900s to their role in today's society, using extensive and sometimes previously unbroadcast archive. Perennially 'man's best friend', dogs are also now man's best colleague. From guide dogs to guard dogs, hearing dogs to healing dogs, Peter examines the ways in which we have become so dependent on canines. Over the years we have progressed from guide dogs to dual purpose dogs, to dogs that can detect imminent epileptic fits, smuggled drugs and explosive devices - even dogs that can do your washing. The programme features a mix of historical material, new interviews and previously untransmitted archive of the trainers, the owners and those that place their lives in the paws of their dogs.