A senior prison warder has resigned after it emerged he broke rules by having lunch with Lord Archer during the disgraced Conservative peer's day release from jail.

Police chiefs in Lincolnshire have also ordered a separate inquiry after a woman police officer attended the same lunch date.

Archer is now in Lincoln Prison

The pair met the convicted perjurer at Zucchini's Italian restaurant in Lincoln, while the millionaire novelist was on a work placement at a local theatre.

Paul Hocking has resigned as head of security at North Sea Camp, the open jail where Archer was being held at the time of the lunch.

On Thursday he was transferred to a closed prison for committing a "serious breach of trust" by attending a party at the home of former Tory Cabinet minister Gillian Shephard.

The female police officer has not been named.

A Prison Service spokesman said: "It is not permitted for serving prison officers to mix with prisoners outside the jail for anything but professional reasons and only with the permission of the governor."

Mr Hocking has a 30-year career in the service before rising to the rank of head of security at North Sea Camp.

What Archer ate

Top Zucchini's items include fillet steak at �15.95 and barbecue king prawns at �13.50 Italian specials include Pollo Prosciuto - breast of chicken in garlic white wine sauce Also on the menu are pizza, spare ribs, vegetable soup and mussels Deserts include chocolate pancakes and profiteroles

Colleagues told the BBC that he should have known it was against the rules to have lunch with an inmate without permission.

And Brian Caton, of the Prison Officers' Association told said on Friday: "For someone as experienced as he was, we find it strange."

Lincolnshire police have asked their professional standards unit to examine whether their officer did anything improper by meeting the convict at the restaurant while off duty on Wednesday.

Lord Archer's wife Mary said her husband was "hurt and angry and bewildered" about being transferred to Lincoln prison, a Category B jail.

She said it was "very sad" that the officer had been forced to resign over a lunch.

"If either of them had thought that would be the outcome, there wouldn't have been the lunch," she told BBC News.

But she added: "It is the prison officer who has contravened a regulation here, there is no reason why Jeffrey should know what prison service regulations are for prison officers."

'Serious breach'

Lord Archer will be kept at Lincoln Prison until jail chiefs complete their inquiries.

The Prison Service spokesman said: "He may be returned to open conditions in due course, depending on the outcome of our investigations and the normal risk assessment made to ensure a prisoner is suitable for open conditions.

Prison Service chief Martin Narey says Lord Archer is being treated fairly

"There has been a serious breach of trust by Lord Archer by not abiding by the terms of his licence.

"We are also concerned about some aspects of his alleged activities while on temporary release in Lincoln."

The peer had been "treated in the same way as any other prisoner", he added.

Lady Archer has said her husband was within "the prescribed 55-mile radius" from North Sea Camp when they called at Mrs Shephard's home in Northwold, near Thetford, Norfolk, 12 days ago.

Lady Archer also insisted her husband did not drink any alcohol during the day.

The former deputy chairman of the Conservative Party was jailed for four years at the Old Bailey in July last year after being convicted of perjury and perverting the course of justice in relation to his 1987 libel trial against the Daily Star newspaper.