DURING the interval of Holy Warriors at Shakespeare's Globe, I checked my Twitter timeline. The breaking news story was that the Islamist militant group ISIS had issued an ultimatum to Christiansin Mosul that they should convertto Islam, or pay a protection tax, flee, or face death. It was impos-sible not to shudder. Towards the end of the first half of David Eldridge's epic new play, Saladin and Richard the Lionheart had both demanded conversion, ransom, or forced marriage as the price ofpeace in the Holy Land. This is a play in which eight centuries of tragic history crash into the present day.

It begins as Saladin (Alexander Siddig, alternately dignified and choleric) sets out to take Jerusalem from Christian hands, convinced that it is the only way to give God the praise he deserves: "What purpose shall Saladin serve beyond the glory of Saladin?" Richard the Lionheart (John Hopkins, brute and coarse, often comically so) responds with the Third Crusade, but cannot retake the Holy City. He dies at the hands of a boy on the walls of a besieged castle.

The first act recounts the 12th-century story energetically, but straightforwardly. Act Two, however, takes the action to purgatory during the 33 years that (according to a 13th-century Bishop of Rochester, at least) it took for Richard to be cleansed from his sins. At this point, the style of the play changes dramatically. In six short scenes,800 years of the history of Western intervention in the Holy Land flash by. Napoleon makes an appearance, followed by Lawrence of Arabia, Golda Meir, and Jimmy Carter. And then the question at the heart of the play is posed: if King Richard lived once more in the 21st century, would he do the same again? And so the hideous battle between Richard's Christian troops and Saladin's Muslim army is replayed, this time with grenades and rifles, shock and awe.

James Dacre's production is constantly engaging, with ferocious battle scenes, dances, explosions, and processions. And the outstanding onstage music cleverly locates each scene in a different culture ora new century. Correspondences between the two halves emphasise (though not particularly subtly) the parallels between the 12th and 21st centuries. Rose petals tumbling from the sky on to Saladin give way to red, white, and blue confetti showered on to victorious Western troops.

But the structure of the play is rather confusing, as past ages collide with present-day realities, and historical facts merge surreally into visionary fictions.

The points it makes are vital, but they are not revelatory. And, for followers of the Prince of Peace, the final prospect of Richard's facing death by readying himself to take the New Jerusalem, through force if necessary, is a daunting one.

PERSEVERANCE DRIVE

is set in the Pentecostal swelter of the Caribbean and the grey grind of north-east London. But its story of the hopes and disappointments of older Christians as their children lose or personalise their faith is recognisable anywhere. It is rare to see a play in which Christian characters live out their faith imperfectly but sympathetically, and the best thing about Robin Soans's family drama is that it is completely believable.

The Gillard family gathers in Barbados for the funeral of Grace, but the service opens explosive rifts among her three sons. Nathan (Derek Ezenagu) and Zek (Kolade Agboke) have become pastors of rival Black Majority churches in London, but the presence of Josh (Clint Dyer) is barely tolerated, because he is gay and has been rejected by the Church.

Nothing is predictable, however. When the location moves to Leytonstone four years later, Zek's congregation has grown into a megachurch, and the once controversial fact that he married a divorced woman has become insignificant. Leading a smaller, local congregation has so absorbed Nathan's life that months pass without his visiting his father; and his wife, Ruth, has become little more than his secretary. (Frances Ashman gives a superb and subtle performance, suppressing a lifetime of wasted opportunities behind a compliant smile.)

But the playwright's sympathies clearly lie with Josh. He has the funniest lines and the tenderest heart. As his proud, pious father (Leo Wringer) becomes frail and lonely, it is Josh on whom he comes to rely. Compassion becomes a stronger bond than family, religion, or moral approval. It is touching to watch, and speaks deep into the soul of any parent who has wondered whether getting a teenager out of bed and into church will really be worth the battle in the long term.

Madani Younis's production is engrossing, and extremely entertaining. The play is more about religion than about faith: we learna lot about the sectarianism that divides the characters, but little about the belief that unites them. Secular Josh is perhaps too obviously saintly. Insensitive Nathan is perhaps too cruelly driven. And the attitude of 1950s Church of Eng-land congregations to Christian immigrants from the West Indies is portrayed as hatred, which misrepresents something that was heartless and cruel, but was caused more by fear than revulsion.

London theatre audiences are predominantly white and secular. Characters in contemporary plays are often given a Christian faith simply to make them unsympathetic, and it is not unusual to hear onstage expressions of faith greeted with groans. Even at the Bush Theatre, the audience initially found the idea of a black man in a purple shirt hilarious, clearly never having experienced the Archbishop of York in full flight. But this first-rate play refuses to stereotype its characters. Faith emerges as positive, and family love as complex; and Christians emerge as fallible. It ends in a quiet hymn of hope.

Holy Warriors runs at Shakespeare's Globe, Bankside, London SE1, until 24 August. Tickets from www.shakespearesglobe.com , or phone 020 7401 9919.

Perseverance Drive runs at the Bush Theatre, 7 Uxbridge Road, London W12, until 16 August. Tickets from www.bushtheatre.co.uk, or phone 020 8743 5050.