Yet, it is a truth universally acknowledged that a single man in possession of a regular prescription for benzodiazepines will sell them on more than one occasion and thus defy his doctor to meet his expectations and her own. Thus, when Nutty McAzepam swears the man at the back of the chemist handing a pharmacy bag to a local dealer for cash was not him but another six foot four Scotsman with dreads I face a quandary.

McAzepam is the type of person who, if told there was a special group on Facebook for criminals, would immediately go to join it. He is not gifted at lying, but then neither am I gifted at accusing him of telling porkies.

Neighbour, Pendleton and Co have turned me into a woman who cannot help but demonstrate trust and partnership, one who irritates her teenagers by being too reasonable.

All of which leaves me stuck for an answer when McAzepam beams through blackened teeth and asks for this week's supply. We like to think consultation models help difficult encounters, but I feel the options are limited to Pendleton (ask about his expectations), Balint (be really nice in the process) or Helman's Folk model (compose a song about the lovely doctor and the wicked patient, backed by a Norwegian violinist in a white nightie and a bevy of transsexual Israeli guitarists, and go on to win Eurovision). And then there is Calgary-Cambridge, where I continuously ask how he feels about what I am saying and what he would like to do next.

I toy with all this and peer at him over my best specs, in the hope that he will wither to a jelly and confess tearfully to selling his stash in the kind of dramatic breakthrough usually restricted to daytime TV.

Several seconds pass. As I search for words that will break the doctor-relationship into a few glittering shards, a broken testament to the great and mighty shared decision making that once was, he adds: 'You think I'm talking bollocks, don't you? I've always been a crap liar. Me mam said.'

Thank heavens for the golden minute. Consultation models are great.

• You can catch up with Mary's Road to Revalidation blog here