"Remember, remember the fifth of November, gunpowder, treason and plot."

Every year we light bonfires, burn guys and set off fireworks to mark the anniversary of the failed plot to blow up king and parliament in 1605.

Now, 400 years on, Edward Kemp has given us a new play detailing the so-called plot in a thought-provoking piece which does what good theatre surely must: To make us think.

He tells the tale more or less as it has come down to us through history. How the evil English Catholics tried to destroy parliament in order to place a Catholic on the throne and reunite Britain with Rome and the old religion.

But history - and life - is never that clear cut and there is very little proof the gunpowder plot of 1605 ever really existed.

Confessions were extracted under torture. The leading conspirators were shot dead as they were being arrested and nothing was ever proved about a tunnel being dug under parliament, nor how much gunpowder was supposed to have been used.

Through this detailed and exhaustive three-hour play Kemp shows the new government of King James I welcomed a Catholic plot. It enabled the oppression of English Catholics, including the imposition of huge fines, to continue and the costly war between England and Spain in Flanders to be brought to an end.

Kemp shows us one of the arch-villains may well have been Sir Robert Cecil, Secretary of the Privy Council, superbly played by Hugh Ross. He was a wily civil servant who made a personal fortune out of repressing Catholics.

His character is ably matched by the Jesuit priest Father Henry Garnett, committed to the overthrow of the Protestant faith and somewhat dissembling in his Roman Catholic morality. Here Richard O'Callaghan gives a powerful performance.

But these two performances are the best of a pretty rum cast of 30, some of whose characters seem peripheral to the main story. Alistair McGowan is disappointing, playing King James as a cheesy, bi-sexual Glasgow comedian.

But there are some good theatrical effects and this is a timely piece with many parallels to the situation in England today.

Running until Sept 8, tickets cost £10-£34. Call 01243 781312.