The French statesman Cardinal Richelieu described it as "the battle that saved civilisation" - the siege of the Hungarian castle of Sziget, 447 years ago, almost to the day.

The Muslim Turks finally took the town in September 1566, but sustained such losses, including the death of their leader, Sultan Suleiman the Magnificent, that they did not threaten Vienna again for 120 years.

Now researchers are digging in the soil - and the archives - for the good sultan's heart....