When the former Ukrainian president Viktor Yanukovych jumped into a helicopter and flew into hiding in mid-February, the Kiev protest movement that had opposed him flung open the gates of his abandoned estate.

Ordinary Ukrainians poured in to visit the 140-hectare grounds and to catch a first glimpse of the luxurious lifestyle Yanukovych had enjoyed at his country's expense. Many gawped at the extraordinary opulence from the gold fittings to the marble floors and the private zoo. But a group of journalists were more excited by a different kind of treasure floating in the nearby lake. Thousands of documents had been dumped in the water by staff when their boss fled. The papers contained proof - not just of Yanukovych's wildly extravagant tastes - but also of systematic bribery, corruption, nepotism and state sponsored violence.

Investigative reporters immediately realised these waterlogged documents could provide crucial evidence for future criminal proceedings. Anxious to preserve them, they worked around the clock painstakingly drying and sorting each sheet of paper. Since then other incriminating papers have been found around the Kiev's city centre. Lucy Ash talks to the journalists on the paper trail and asks why divers, archivists, lawyers, accountants and so many ordinary volunteers are eager to help them.