Four years ago this week martial law was imposed in Poland and the short-lived free trade union movement Solidarity was suppressed. Panorama has been back to Poland to discover that the underlying economic problems that fuelled the rise of Solidarity are as great as ever. The movement itself lives on underground, with the Church as the shield and the focus for the opposition. Robert Harris has talked to top Government ministers and to Solidarity leader Lech Walesa who is deeply pessimistic about Poland four years on from martial law.