'Never mind. Maybe another time,' the driver said, with a sigh of resignation. 'But that's not all,' I replied. 'I need you to give me a loan.' It was true. If I didn't catch a waiting ferry across the Marmara Sea to the Princes Islands, I would miss interviewing the Armenian patriarch. And I didn't have a Turkish lira to my name for a ticket.
'How much do you want?' the taxi driver gamely said. I asked for 50,000 lira (pounds 3). 'Are you sure you don't need 100,000? It's no trouble at all.' I gave him my card, he gave me the money and his phone number. His name, Sefer Yildirim, did justice to my sense of gratitude: translated bluntly from the Turkish, it means Journey Thunderbolt.
Perhaps one finds this degree of trust in many places, but I doubt it. Istanbul taxi-drivers are a forgiving lot, considering their 12-hour shifts in flocks of box-like, Turkish-built yellow Fiats. Even though there have been recent improvements with lights, the traffic is also still some of the world's most polluting and dangerous. About 15 people die in Turkish road accidents each day - more than in the insurgency in Turkey's mainly Kurdish south-east.
No group of people is perfect, of course. A few jackals plague Istanbul's tourist districts and the international arrivals sections of Istanbul airport is mostly milked by monolingual cheats whose unroadworthy vehicles have been assigned there by one of Istanbul's many mafias.
One reason is that a taxi with a licence costs about pounds 60,000 and is generally bought as an investment by merchants or professionals. The drivers themselves are often uninsured journeymen on their first job in the big city, thus ensuring an almost total ignorance of the Istanbul's cartography.
Even experienced chauffeurs say there is no way they can get any 'knowledge'. Many streets do not have names and the concrete sprawl of Istanbul now measures about 100 miles from east to west to cope with a population that has grown to 10 million in a matter of decades.
But I am writing about the silent majority of taxi drivers. And everybody in Istanbul has a story of some extraordinary act of taxi honesty in the school of 'my aged mother's lifetime collection of jewels were returned after we left them in a bag at the back of the taxi'.
The phenomenon is all the more extraordinary when compared to the dishonesty of public officials, building contractors and city grandees, as well as a general get-rich-quick rush of conspicuous consumption by the wealthy elite.
Most Istanbul taxi-drivers now start their meters correctly. They rarely expect a tip. When giving change, they habitually round the fare down. One friend is never asked for payment by his local taxi-driver, an act of gratitude, apparently, for some past favour.
I thought I had done well when a taxi-driver in Ankara returned my wallet and identity cards by post, although without the money. Then my wallet fell between the seats of an anonymous taxi as I got out at an Istanbul hotel. I had not even noticed until, an hour later, a page-boy interrupted a press conference to call me outside to where a driver, after a long argument with the hotel staff, finally handed me back my wallet with hundreds of dollars intact.
He accepted the reward I pushed hastily into his hand. But the man who saved my trip to the Princes Islands, Mr Yildirim, was even more scrupulous when he dropped by to pick up what I owed him the next day. I had left a 50 per cent tip, but he refused it. He simply wanted his due.