SIR Peter Harding, Chief of the Defence Staff, resigned last night

after allegations of an affair with the young Spanish former wife of a

former Defence Minister.

Britain's senior military officer quit after the publication of

intimate details of his relationship with Lady Bienvenida Buck appeared

in the News of the World.

The Ministry of Defence said: ''Marshal of the Royal Air Force Sir

Peter Harding, Chief of the Defence Staff, has tendered his resignation

with immediate effect.

''This has been accepted by Malcolm Rifkind, Secretary of State for

Defence.''

News of the affair between Sir Peter, 60, who is married, and the

former wife of Sir Antony Buck rocked the Ministry where the military

chief was seen as a single-minded career officer.

Tall, debonair, and articulate, he had worked his way studiously to

the top, taking a number of key appointments, including one at Nato's

Shape military headquarters.

Mr Rifkind had defended Sir Peter, saying he had ''total confidence in

the professional abilities of his Chief of the Defence Staff''.

However, once it was known that the News of the World had videos, tape

recordings, and letters relating to the affair, the full impact was felt

and Ministry officials said Sir Peter had no option but to quit.

Adultery is viewed as a serious transgression of traditional values

within the Services, where marriage and family life are revered. The

military has recently launched its own back-to-basics code of conduct

for officers and men.

One official said: ''How could he continue when on the one hand he was

calling for better standards of personal behaviour while on the other he

was having this affair?''

When the news of Sir Peter's resignation was broken to Sir Antony he

gasped and said: ''I am sad about the fact that he has resigned and in

all the circumstances it is understandable, but regrettable.

''I think it is absolutely tragic because he is a brilliant officer.

It is a great shame that what has happened about this matter has caused

this to happen.

''I am, naturally, sad about it, but given the background you cannot

expect me to be overwhelmed with grief. I am sad and for Sheila, his

wife. It is a miserable time for us all.''

Former Navy Minister Sir Antony, 65, retired from the House of Commons

at the last General Election. He married Bienvenida Perez-Blanco, some

30 years his junior, in 1990. The marriage broke up last September.

The Liberal Democrats' defence spokesman, Mr Menzies Campbell, said:

''To become Chief of Defence Staff, a man needs outstanding abilities.

''Sir Peter Harding had those in full measure, and so long as his

ability to do his job was unaffected, I can see no reason why he should

have resigned.''

Labour pressed ahead with its demand for an inquiry to ensure that Sir

Peter's affair did not give rise to any security lapses.

The Shadow Defence Secretary, Mr David Clark, said: ''He has done the

right thing. But I am still writing to Malcolm Rifkind to demand an

inquiry to establish that there has been no security lapse.

''This man knew all our military secrets and one must be absolutely

certain that there have been no lapses in our security.''

Copies of Sir Peter's letter of resignation to Mr Rifkind, and the

Defence Secretary's reply, were issued last night by the Ministry.

Sir Peter wrote:

''You will have seen the

news reports concerning me and Lady Buck. The content of these reports

is not entirely right and there are some errors in them, but it is

counterproductive to relate them in detail. The point is that I have not

acted in a manner that befits the holder of the post of Chief of the

Defence Staff.

''I therefore believe that the only honourable thing for me to do is

to resign my post with immediate effect, and I ask you to accept this.

''I deeply regret the embarrassment that this has caused for you, the

Government, my colleagues, and the Services; and I am grateful for your

support over the last 15 months, which has been considerable.''

In reply, Mr Rifkind said:

''I am very saddened that recent circumstances have led you to reach

this decision; but I understand and respect your wishes.

''May I pay tribute to the many years of dedicated service that you

have given to the Royal Air Force and the Armed Forces. In your earlier

career, as Chief of the Air Staff, and again as Chief of the Defence

Staff, you have exhibited professionalism, energy and skill of a very

high order.

''I very much regret that we will no longer have the benefit of your

advice and judgment. I know that you feel that your resignation is in

the best interests of the Royal Air Force and the Armed Forces and that

is, if I may say so, characteristic of the loyalty and commitment you

have always given to your colleagues.

''May I offer you and Sheila my very best wishes for the future.''