The Duke of Northumberland's daughter has been banned from the roads after she was clocked doing 115mph displaying her "advanced" driving skills.

Lady Catherine Sarah Percy told a court she was tired and needed to get back to her picturesque Alnwick Castle home.

So the 19-year-old floored her £20,000 Chrysler PT Cruiser on the A1 believing there was a clear road ahead.

But she did not see a traffic cop with a hand-held speed camera who trapped her doing 45mph over the limit.

Lady Catherine, the eldest daughter of Lord Ralph, 44, and Lady Jane, 43, admitted speeding but told the court she had had "advanced" driving training.

But magistrate's said the training should have made her realise that speeding was dangerous.

Lady Catherine was caught as she sped along the A1 at Cawledge Park near her father's ancestral home on February 24.

She appeared before the town's magistrates on Wednesday, wearing a sart trouser suit and trainers, and admitted speeding.

The court heard how on the day of the offence she was tired and keen to get back home to her castle, which has been the seat of the Percy's since 1309.

In mitigation, solicitor Richard Wormald said the weather at the time was fine and she had found herself on a clear stretch of dual carriageway with little traffic and her speed climbed as she neared home.

He went on to say Lady Catherine had taken two further driving courses since passing her test at the age of 17, on the insistence of the duke and duchess.

She had already completed a 10-hour "pass class" which covered driving in adverse conditions and was currently awaiting a test for her advanced driving licence, having already completed all the theory.

He told magistrates: "She is somebody who is willing to be responsible in terms of road use.

"She is living at home but she is trying to get a job with Bonhams the auctioneers' classic car division and she is going to be required to drive some expensive and classic cars.

"She cannot go to work while she is disqualified and she recognises this is a serious offence."

But magistrates were not swayed after it was that Lady Catherine already had three penalty points on her licence for speeding in March last year.

Magistates banned the teenager from driving for 28 days and fined her £200 and ordered her to pay £55 costs.

Chairman of the bench Colin Dixon said disqualification was inevitable.

He said: "This was an extremely high speed, 45mph above the speed limit. We have been told the road was clear, but anything could have happened.

"We would have thought that having taken extra driving courses, you would have realised this kind of sped was dangerous."

Lady Catherine declined to comment after the hearing.

Her parents, who have two sons and daughters and are beilieved to be among the richest people in Britain worth an estimated £300m, were not present at the short hearing.