It is a late May evening and Sergei Pugachev, the exiled Russian tycoon, is flicking through an old family photo album. In one photograph, Mr Pugachev’s son, Viktor, is captured with eyes downcast as Maria Putina, the Russian president’s daughter, leans to whisper in his ear. In another, Mr Pugachev’s other son, Alexander, is posing on a wooden spiral staircase in the Kremlin library with Vladimir Putin’s two daughters. At the edge of the photo is a smiling Lyudmila Putina, then still the president’s wife.The two families were close. Mr Putin’s daughters would often come to the Pugachevs’ house from the president’s neighbouring residence outside Moscow after school.