The Percy family home is Alnwick Castle in Northumberland

Lady Catherine Percy, 21, was already serving her second ban from driving when her case came up before magistrates in Newcastle on Thursday.

She has been warned by her parents, the Duke and Duchess of Northumberland, about her behaviour on the roads.

Lady Catherine, of Alnwick Castle, Alnwick, Northumberland, was once banned for 28 days after police recorded her doing 115mph in her Chrysler PT Cruiser.

She was not present in court on Thursday but in a letter to Newcastle Magistrates' Court she pleaded guilty to the speeding offence on 17 February, and apologised.

She was fined �75 and ordered to pay �75 costs as well as being given four penalty points on her driving licence.

Driving ban

The motor-racing enthusiast had been caught by a speed camera driving at 41mph on the B318 Great North Road on the outskirts of Newcastle.

She was given a six-month ban by magistrates in Harrogate for breaking the 70mph limit at the A1M at Boroughbridge, North Yorkshire, on 5 May, 2003.

On 7 May, the case involving her speeding on the B318 was heard for the first time, but was adjourned, before finally being resolved on Thursday.

A spokesman for the Duke of Northumberland issued a statement saying: "Lady Catherine accepts the court ruling and apologises for her excessive speeding.

'Public roads'

"Lady Catherine, who is mid-way through a three-year car mechanic course, has a keen interest in motor racing.

"The Duke and Duchess have accepted their daughter's apology, reminding her that speed on the track should not be duplicated on public roads."

The Duke and Duchess, who have two sons and two daughters, own land, homes, art treasures and other assets worth an estimated �300m.

Last year, more than 120,000 people visited their home, Alnwick Castle, seat of the Percy family since 1309. It has featured in recent Harry Potter films.