The Earl of Stockton, the grandson of a former British Prime Minister, has been banned from driving after he crashed his car while drunk.

Alexander Macmillan, the 79-year-old descendant of Harold Macmillan, admitted to a charge of drink driving at Wycombe Magistrates' Court yesterday (Tuesday).

Lord Stockton failed a breath test after he crashed a black Range Rover into two parked cars in Old Mill Road, Denham.

The hereditary peer was on his way to his Denham home after leaving a nearby event at around 5.30pm on July 31.

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The court heard from the prosecutor how Lord Stockton had skipped lunch that day before he "drank some wine" at the event.

On his way home, Lord Stockton swerved into the parked vehicles. The court heard how minor damage was caused to the cars.

Police were called to the scene, and after he failed a breath test the officers took Lord Stockton into custody at Maidenhead Police Station, where he gave a reading of 42 micrograms of alcohol in 100 millilitres of breath. The legal limit is 35 micrograms.

The court heard how Lord Stockton, a former Conservative member of European Parliament, was "extremely sorry" for what happened and regretted the "poor decision" he took to drive home that day.

The Denham resident, who also spent some time on the South Bucks District Council after he was voted in 2011, pleaded guilty to the charge of drink driving levelled against him.

After the magistrates heard the evidence, Lord Stockton was fined £7,616 and told to pay £2,085 in costs.

The large fine was imposed to reflect Lord Stockton's substantial income. The Earl has appeared on the Sunday Times Rich List in the past, and in 2009 was estimated to be worth £160 million after he sold the Macmillan publishing group. 

Lord Stockton was also given a 13-month disqualification. This can be reduced by 13 weeks if he completes a driving awareness course.