Mamma Mia, here we go again: spooky echoes of the 1970s just keep on coming. Gordon Brown is in Japan at the summit of the Group of Eight leading industrial nations discussing the oil crisis. It was in the wake of an oil crisis and subsequent recession that the first summit of the original Group of Six was held at Rambouillet, near Paris, in November 1975 – two months before Abba reached number one with the song that inspired the recent musical, the film version of which opens in the UK this week.