Holwood House, Keston

The seven-bedroom Holwood House in Keston, Kent, boasts 40 acres of land as well as views of Canary Wharf

William Wilberforce, Winston Churchill and Charles Darwin were all regular visitors to the property

The house was bought by Pitt the Younger for £8,950 in 1785 while the current owner spent £2.5 million in 2002 

Mr Pitt and William Wilberforce sat under an oak tree in the grounds and discussed the abolition of slavery

A luxury stately home where the campaign to abolish Britain's slave trade took shape has gone on the market for £12 million.

Holwood House, in the village of Keston, Kent, was not only once owned by a former prime minister, it can also boast of hosting Sir Winston Churchill for regular lunches and having had Margaret Thatcher as a close neighbour.

The sprawling seven-bedroom mansion is dubbed 'the original Chequers', and has the price tag to match its illustrious history.

Its former owner, William Pitt the Younger, who became the youngest Prime Minister in 1783 at the age of just 24, paid just £8,950 for the house in 1785 despite his 'consistently unsteady finances.'

It is said to be where Mr Pitt and his friend and fellow politician, William Wilberforce, sat together under a large oak tree in the grounds and discussed the abolition of slavery.

On 12 May 1787, Mr Wilberforce wrote in his diary: 'At length I remember after a conversation with Mr Pitt in the open air at the root of an old tree at Holwood just above the steep descent into the vale of Keston, we resolved to give notice on a first occasion in the House of Commons of my intention to bring forward the abolition of the slave trade.'

Set in 45 acres of landscaped gardens and rolling parkland and surrounded by trees, the Grade I listed home is within sight of the City of London.

Situated well within the M25 and 14 miles from the heart of the capital's financial district, the historic property will provide its new owners with a relatively easy commute to work.

It used to be owned by Edward Stanley, the 15th Earl of Derby and Secretary of State for Foreign Affairs who commuted to Westminster from there.

The mansion is currently owned by Martin Zapico, a retired investment banker, who has had it refurbished to a high standard. 

In 2011 he let it out as a film set for the children's movie Horrid Henry.

It boasts a stately entrance and grand sweeping staircase, a library, study, newly refurbished cinema room, tennis court, walled garden and garden pavilion.

Edward Rook, a partner of estate agents Knight Frank, said: 'A lot of people, especially international buyers, aspire to a fine English country house but more often than not the compromise is a two hour-plus commute or having a place in town during the working week and a country house at the weekends.

'This house allows you to have those two houses and lifestyles in one - it works both as a town and country house.

'To have a property that sits in its own country park of 45 acres and yet is just 14 miles from Canary Wharf is remarkable. Properties of this size within the M25 are usually owned by organisations like the National Trust.

'We expect a high net-worth family who are cash rich but time poor to be interested in this property.

'There are some great private schools close buy, a Michelin star restaurant and Biggin Hill airport because if you are a high net-worth family private jets are a reality.'