Purdey comes to Westminster.

Keith Vaz’s Home Affairs Committee is generally accepted as Westminster’s equivalent of a television chat show. Passing celebrities coming within the faintest orbit of the committee’s investigations are invited to give evidence.

They’ve had Cherie Booth on knife crime and Jesse Jackson on drugs so an appearance by Ab Fab star Joanna Lumley should have left members unphased, even if they had been passing around police Tazer gun beforehand Don’t ask, it’s that kind of committee. She certainly didn’t leave them unimpressed.

Joanna Lumley, the Gurkhas’s sweetheart, sat demurely on the public benches, waiting her turn as two Ministers poffered their excuses for not granting UK residency to the Nepalese fighting men.

The Commons had voted against their restrictive proposals so they tried their best to co-operate with the committee to find a way forward, without conceeding an inch.When the drab gents from the Ministry had departed she soothed the committee in breathless tones, befitting a TV goddess. The words were soft but deadly, clear and compelling. She was a hot-bobbed Purdey, not a shambolic Patsy.

Lumley is, after all, a battle-hardened politician - the only person actually brave enough to wave a sharp instrument near Mr Brown’s, er, Schools Minister. Like a good politician she made every word count. She vowed to "stick to her guns" and fight on for parity of pay, pension and settlement rights for all Nepalese soldiers who have served British Army.

She revealed she had written to Prime Minister Gordon Brown on the issue three times and received only one reply, from a secretary.Great beauty can be a curse but Ms Lumley uses her grace and her looks to great effect. She was self-effacing about being a pensioner, she turned 63 last week, to drive home the point that Gurkha WWII veterans would be too old to settle in Britain. At one point she feared she might be mumbling (she is not a trained actor) simply to allow MPs to assure her she wasn’t. She flattered these "brave" Labour members who had rebelled last week. Mr Vaz didn’t even blush at that, he probably thinks he is brave.

She delivered a stirring rallying cry and namedropped a member of the Royal family as a supporter without breaking confidences. That was about five news stories in as many minutes, all dropped in with cut-crystal, faux bewilderment. "I do not know what we have to do. I don’t know where else we have to go," she said. "We have gone to the High Court, we have gone to the press, we have gone to the people and to parliament. Where do we go to?"

Beside her sat Lieutenant Mada Gurling, whose father had served with Ms Lumley’s father in the 6th Gurkha Rifles. He confirmed that the economic effect of migrating Gurkhas would be minimal on Nepal and she said Gurkha officers like him, many of whom qualify for admittance under the new rules, would refuse to come to Britain if their men were left behind.

The government had fired its volley first, claiming the economic effect on Britain would be devastating. Kevan Jones, a Junior Defence Minister, feared allowing all the Gurkha soldiers in would open the door to a huge pension bill, £1 billion initially, plus annual payments of £500 million."Political populism doesn’t change the facts," said Phil Woolas, the Home Office Minister, only slightly humbled by the Commons vote to meet a debt of honour.

Ministers had inflated both the number of Gurkhas hoping to come to Britain and the cost, Ms Lumley said. Labour MP Martin Salter revealed the Government’s own estimates put the cost at as little as £425 million. Ministers were quoting the highest possible estimate of £1.6 billion, he said.

"We think scare tactics have been employed here. We stick to our guns and say ‘Equal rights for Gurkhas and parity with Commonwealth soldiers’," said Ms Lumley. She said it gently. "It doesn’t seem very extreme when you say it like that," she purred. Utterly charming and, as the government already knows, totally lethal. The MoD shouldn’t mess with Purdey.