Assistance Dogs are important for many different reasons. Here is what to look for.
Does the dog’s jacket have the ADUK symbol?
Does it say Please do not distract? This is most important as it is a working dog not a pet. This means the dog is focussed on its work and the Partner is dependent on that. Please ignore the dog. I know it is really hard, and they look so soft and touchable, but it is SO IMPORTANT that you ask permission. Distracting the dog makes it forget what it was doing. Wait until the Partner gets the dog prepared to say hello, and then the dog can really enjoy the meeting of you. Distraction stops the dog from working and limits its concentration.
Check out the information on Assistance Dogs If they are a member of ADUK http://http://www.assistancedogs.org.uk/ they are a member of a coalition of assistance dog organisations that encourages the exchange of ideas and best practice amongst its members, raises awareness amongst the general public and promotes behavioural and legislative changes to ensure the freedom, independence and rights of its clients.
My Assistance Dog, Alucia, is trained by Canine Partners http://www.caninepartners.org.uk but the ADUK website will give further information of other assistance dogs. All members of ADUK hold registration documents which allows a dog to visit restaurants, and other food outlets. They are properly trained to work in areas pet dogs are not allowed to enter.