Jacob Walker had his home in Highgate and lies buried in Hornsey. Yet he lived much of his life as a slave. Indeed, the inscription on Walker's grave chillingly records that he had been a "faithful slave" – though how he would himself have described his own status, we'll never know.

The interment is in the grounds of St Mary's, Hornsey – a churchyard without a church, though it does have a spectacular 15th-century church tower which has been retrieved from dereliction and the depredations of many generations of pigeons by the Friends of Hornsey Church Tower.

Thanks to these resourceful volunteers, the vestry room at the base of the tower is once more a chapel. It can also be hired as "London's smallest and coolest performance space". The conditions of use specify, intriguingly: "It is not available to hire for pop videos for gothic rock bands."

The tower is – in normal times – open several times a year to those who can face the 120 spiral steps.

Ham & High: The church tower at St Mary's, HornseyThe church tower at St Mary's, Hornsey (Image: Andrew Whitehead)

The Friends of Hornsey Church Tower have also tidied up the churchyard and compiled a guide to some of the more interesting of the graves, among them that of Jacob Walker. He is one of two people interred together.

This is the inscription on the gravestone: "Harriet Long / a native of Virginia / the widow of Joseph Selden / Lieutenant Colonel in the army / of the United States / and the wife of George Long / died at Highgate / on the 18th day of June 1841 / in the 40th year of her age."

There are then a few lines in Latin in the form of a mourning epigram – George Long was a professor of ancient languages at the University of Virginia for four years in the 1820s, which is when he met Harriet.

And then comes a record of a second interment just two months later: "'Jacob Walker / a native of Virginia / in America the faithful slave / in England the faithful servant / of / Harriet and George Long / and an honest man / died at Highgate on the 12th of August 1841 / in the 40th year of his age."

It's likely that Jacob Walker was an enslaved member of Harriet Long's Virginia household and on her second marriage moved with her into the new marital home.

When he moved with his master and mistress to England in 1828 – the family lived in Jackson's Lane – his legal status changed from slave to servant, though what difference that made to his freedom of action and daily routine, we just don't know.

By the time Jacob Walker walked ashore here, slavery was illegal. A court case in 1772 had ruled that slavery was unsupported by common law in England and Wales. That would have affected several thousand people of colour in England and Wales, most working in domestic service.

Britain "abolished" the slave trade in 1807 and slavery was ended across the British Empire (except in much of South Asia, where it persisted legally for another decade) in 1833.

The British government put £20 million aside – that's an astonishing £2.3 billion in today's money – to compensate not the slaves but the slave-owners.

Ham & High: The chapel at St Mary's, HornseyThe chapel at St Mary's, Hornsey (Image: Andrew Whitehead)

On top of the deeply unsettling description of Jacob Walker as a "faithful slave" is the exceptional interment alongside his owner/mistress – hardly the routine way of burying either an enslaved man or a household servant.

One account from the 1920s recorded that "an old black servant [Harriet] had brought with her from Virginia, was found dead on her grave a day or two after her funeral, so the grave was opened that he might be buried with his mistress". A nice yarn, but apparently not true. Harriet died from cancer. Jacob succumbed two months later to what was recorded as "smallpox after vaccination".

The shared grave suggests a strong bond between Harriet and Jacob, who enjoyed something approaching parity of esteem in death even if that had eluded Jacob in life. The widower, George Long, was clearly responsible for the funeral arrangements and the words on the gravestone.

"The symmetry of the inscription reflects the poignant symmetry of the two lives," Historic England has commented, adding: "It seems that [George] Long wished to draw attention to this."

George Long's own attitude to slavery can only be surmised. He was brought up in Lancashire where his father was a West India merchant, and so inevitably caught-up in one manner or another with slavery. George himself was sympathetic to the pro-slavery southern states (which included Virginia) in the American Civil War. The United States abolished slavery only with the defeat of the Confederate states in 1865.

Jacob Walker's gravestone is one of a small number of British memorials and monuments linked to slavery and emancipation that were given listed status on the bicentenary of the 1807 Abolition Act. It's a small acknowledgment of an unconscionable wrong. And a reminder that slavery left its mark not just in the plantations, not simply in the slaving ports, but here in North London too.

Andrew Whitehead is a local resident and historian and the author of Curious Crouch End, which is being published imminently.

Ham & High: The inscription for Jacob Walker and Harriet LongThe inscription for Jacob Walker and Harriet Long (Image: Andrew Whitehead)