Turkey (Time to process: 1 hour)
A new office is under construction. The existing Turkish border is a dust bowl yard, with a series of old Portacabins and polythene tented rooms.
First process the visa in the Portacabin. Then have the vehicle processed by two customs personnel in the polythene tented room. The vehicle's chassis number was checked.
Customs "surcharge" - 2 million TL.
Iran (Time to process: 3 hours)
New offices, well organised and friendly.
Visa checked first in the little booth on the left of the entrance doorway to the main hall (accessed through the chainlink fence).
A customs officer travelled in the vehicle from the entrance compound (just through the border fence/gate) to the checking compound (around the back of the customs hall).
Back in the main hall, complete a customs form for personal effects. Then process the vehicle with the Carnet de Passage.
The vehicle is checked for chassis/engine number and contents. The Carnet is stamped in a small office to the south of the main hall. Also get a piece of paper from this office. Back into the main hall, Carnet checked. This is the customs cleared...
... but not the end of the paperwork.
Take the vehicle down the hill towards the town in the distance. There is an Iran Insurance office here on the left (large sign in English over the top). 1 month insurance costs 192,000 IR (GBP 18).
Go to the office 50m further down the road from the insurance office. Go in, smiling and looking dumb - somebody will help you. They check your paperwork and enter your details in a huge ledger.
Back into the vehicle and to the exit gate, operated by the police. They require a photocopy of your documents, which you have to obtain in a shop on the main road in Iran proper. More ledger entering, and then you're free to go.
No charges going through the Iranian part of the border.