"Good Lord!" Robert Gordon exclaimed, looking up at the plaque in Khartoum's Republican Palace where his ancestor, General Charles Gordon, was killed 129 years earlier by the forces of an Islamic reformer called "the Mahdi".
On Friday, one of the Mahdi's descendants, Abdel Rahman Sadiq Al-Mahdi, accompanied Gordon on a visit to the building where his uncle -- many generations removed -- lived, worked and died.
The Mahdi's conquest of Khartoum despite Gordon's efforts to defend it is a defining moment in Sudanese history, forming the basis of the 1966 film "Khartoum". It starred Charlton Heston as Gordon and Laurence Olivier as the Mahdi, whose real name was Muhammad Ahmad.
"Charles George Gordon. Died 26th January 1885," reads the memorial on a wall of the palace where President Omar al-Bashir has his offices.
Robert Gordon, 63, said his meeting with the descendant of the man whose troops killed his ancestor had been a "complete surprise".
Gordon, a retired British general, works in Baghdad with the United Nations and previously led a UN peacekeeping mission for Ethiopia and Eritrea.
He has spent several days in Khartoum explaining the role of UN peacekeeping to Sudanese security personnel and diplomats, an effort funded by the British embassy.
It was his first visit to the country in four decades.
In a chandeliered reception room at the palace, originally built in the early 19th century during Turco-Egyptian rule, Gordon and Abdel Rahman Sadiq al-Mahdi talked about the building that has been so important to both their families.
Abdel Rahman Sadiq al-Mahdi, dressed in his traditional white turban and grey waistcoat, works as an adviser to President Bashir in the old palace, which Mahdi said is to be turned into a museum when the government moves into new offices nearby.
The palace, a whitewashed three-storey structure that recalls Britain's colonial past, contrasts with the heavy-looking grey-brown stone of the new presidential offices under construction.
"Lovely to see this building," Gordon said as a waiter served glasses of red karkade, a drink made from hibiscus which he had not tasted since the early 1970s when he spent four summers in Sudan while studying at Cambridge.
Key moment in Sudan's history
From 1877-79 Robert Gordon's ancestor Charles George Gordon served the Turco-Egyptian administration as governor of Sudan "to fight the slave trade and organise the administration of those lands," Sudanese historian Mandour El Mahdi wrote.
After the British occupied Egypt in 1882 and the Sudanese Mahdist revolt intensified, Britain again dispatched Gordon, a general who had already made his name in China.
He reached Khartoum in February 1884 and met his death a year later when the Mahdists seized the garrison before British reinforcements could arrive.
"With the fall of Khartoum, the Turkish regime in the Sudan was over," Mandour El Mahdi wrote.
Asked his feelings about meeting a relative of the man responsible for killing his distant uncle, Robert Gordon told reporters: "That's the risk people ran in those days... Mind you, he was here to help. If you know the history, Gordon was a good man."
Britain and Egypt later defeated the Mahdist state and jointly ruled Sudan from 1899 until independence in 1956.
For much of the time since, Abdel Rahman's father Sadiq al-Mahdi, the great-grandson of the Mahdi, has been a powerful figure in Sudanese politics.
He led a coalition government overthrown when Bashir took power in a 1989 Islamist-backed coup, and still heads the opposition Umma Party -- while his son Abdel Rahman serves the government.
For the Mahdis, politics runs in the blood. For the Gordons, it is soldiering.
Standing below the memorial to his relative, Gordon told Mahdi about his son, a British soldier who just finished a tour of duty in Afghanistan.
"My son is called Charles Gordon and he was born in 1985," a century after another military man known as Charles Gordon lost his life in Sudan.