Theresa May has presented Crown Prince Mohammed bin Salman with an antique family tree showing the descent of the al Sa'ud dynasty of the kings of Arabia.
Downing Street said the framed document was originally created by Queen Victoria's consul general in Jeddah in 1880.
"The PM thought it would be a nice and appropriate gift to give," the Prime Minister's official spokesman said.
Mrs May hosted the Crown Prince for a private dinner at Chequers, her official country residence, on the second day of his official visit to the UK.
They were served halibut with cucumber, radish and lemon, followed by Chiltern lamb rack with lamb shoulder broth and new potatoes with dessert of Yorkshire rhubarb cheesecake with ginger.