Two problems have been resolved at the last minute, both concerning visas – one with a capital V, the other a small one, though this does not reflect the importance of each problem.
The big problem is the visa! After a dozen unanswered phone calls, several emails and two trips to the consulate of the Iranian embassy in Paris (including one when I was accompanied by an Iranian friend whose family has very kindly offered to vouch for us), I finally got confirmation today that my visa application has been approved. I don't have an actual visa yet, but I have an authorisation number that will allow me to get one on arrival in Tehran.
The other issue is my Visa card. I changed banks a few months ago and have only in the last few days received my new card. It's no use in Iran but will be much used and abused in Turkey and whatever other countries I visit before I travel back to Paris.
Next post from Tehran – airport, jail, hotel or cybercafé... we'll see!