Bingowings said:

When I needed to make an insurance claim and have my student loan demands stopped the consultant treating me draughted a signed letter which had all the necessary details and was dated.

It would be useful to have such a document for general use anyway but it would certainly come in handy in this instance.

I have the same type of letter for my service dog, and also for my medical cannabis use. All my doctor did was write a basic letter saying that I am under his care for a life threatening illness. The two of us signed it, giving a sort of limited permission to check up on this letter. The doctor will make a copy for his files.

So now, If I go into a club to buy cannabis, the office staff of that club WILL call the doctor's office to see if I truly am under that doctor's care, and if that letter is legit. The doctor's office will give no further details. In a sense, the letter is the permission to verify I am under treatment of some kind.