The temptation to turn Mr Knightley into a conventional romantic lead is hard to resist, but adapters who succumb fatally diminish the book's moral force. 

Criticising the current BBC series feels like clubbing an invalid who is recovering from assault and battery. BBC documentaries remain as shallow as they have been for years, but the drama department is showing encouraging signs of emerging from the asinine populism Greg Dyke inflicted on the corporation. Before I go any further, I must therefore say in kindness that Emma is well made and beautifully acted. Romola Garai's eyes widen with delight as her mind hits on a matchmaking project. Jonny Lee Miller (Mr Knightley) gives a star-quality performance. And any supporting cast that includes Michael Gambon will always be worth watching. And yet, the best actors in the world could not save this production. Kate Harwood, controller of BBC serials, announced that she did not want "stuffy period characters" but a fresh, modern Austen. "The casting of Romola and Jonny is an absolute joy," she purred, because of the "tremendous chemistry" between them.

Indeed there is. So much chemistry, in fact, I was surprised they did not spontaneously combust. In an opening scene, Mr Knightley upbraids Emma, and she turns to face him with a glittering come-hither smile on her face. By the end of the second, she is showing visible signs of jealousy at the thought he may be in love with someone else.

The viewer cannot blame her because Jonny Lee Miller does not look almost twice her age or even five years older than she. He is just as attractive as the dangerously seductive Frank Churchill whom Austen dangles
before Emma — and much, much richer. Far from being the culmination of a search for self-knowledge, Emma and Knightley's marriage feels inevitable from the start — two young, beautiful moneyed people shack up, what could be more natural? The BBC may be pleasing modern tastes, but by removing the stuffy period characters and promoting sexual chemistry, Harwood has not produced a fresh adaptation, but a lifeless drama, with the tension drained out of it. 

Before he died, Dennis Potter told how delighted he was when Hollywood bought his Pennies from Heaven. The producers flew him to a luxurious apartment and asked him to write a new screenplay. They took it from him and said they needed a rewrite. Potter complained, so they gave him more money. The rewritten script was rewritten again and again, and every time the producers gave Potter more money. They then tested the finished film with trial audiences who did not like it, so the producers cut it before general release. By the end, Potter was considerably wealthier, but the Hollywood version of Pennies from Heaven bore no relation to his story.

Potter was baffled. Why had the studio bosses bought his drama in the first place if they did not want it? The same question haunts the latest Emma. If the BBC thinks Austen too stuffy, why bother to adapt her charming but surprisingly tough novel?