Thursday should see Poland basking in history as it commemorates the 20th anniversary of June 4 1989 – the day elections ended Communist party hegemony and helped set off changes that freed central Europe from Soviet domination.

But instead of celebrating, Poles have become entangled in fights between government and opposition, protest threats by disaffected workers gathered under the hallowed banners of the Solidarity trade union, and arguments over the legacy of 1989, extending even to questioning the role of Lech Walesa, the Nobel prize-winning former president and Solidarity’s first leader.