At Kol Nidre this year, a visitor would have been able to walk into Hendon United Synagogue in north-west London and comfortably find a seat. Twenty years ago, for one of the 25 biggest congregations in the country not to have been full would have been inconceivable.
I first met Mark Sofer in a humid Mumbai car-park in November 2008. The multiple terror attacks on the city - which included an assault on a Chabad centre - were still in progress, Israeli security teams were scouring mortuaries to discover how many of the country's nationals had been killed, and the Israeli ambassador had agreed to give an impromptu briefing to reporters outside the consulate.
I was looking at a photograph of George Best when I had my eureka moment.
It was 1968 and, as a young entrepreneur in my 20s, I was running a company called Star Posters, which had just launched a series of products aimed at the new, affluent youth market - Frank Zappa sitting on a lavatory seat, Jimi Hendrix "making love" to his guitar.
Theodore Zeldin believes conversation has the power to change the world. Not a chance remark, and certainly not small talk, but the kind of meaningful exchange of ideas we tend deliberately to avoid in social situations.
Now the celebrated philosopher and historian is travelling the world holding talk-fests where people begin to discuss a topic with a complete stranger,