The stone time capsule was presented to the US last week during a ceremony involving Virginia governor Glenn Youngkin and first lady Suzanne S Youngkin.
The capsule is made of Portland limestone taken from one of the original steps of the George Washington Statue plinth in London, which had its limestone replaced during a restoration overseen by Fosters last year.
It contains student design competition entries, proclamations and letters from senior US and UK public officials, a list of stakeholders and donors, and proclamations and letters from US president Donald Trump and King Charles III.
It includes instructions to be reopened on July 4, 2276, when the US is set to celebrate its 500th anniversary.
The outside of the time capsule is inscribed with 13 six-pointed stars replicating the design of George Washington’s famous Headquarters Flag.
President Trump’s administration is expected to bury the capsule later this spring under the plaza at the Washington Monument as part of the country’s 250th anniversary celebrations, the Virginia governor’s office said.
The time capsule is the twin of one placed under the fully restored George Washington Statue in London’s Trafalgar Square as part of the Friends of the Washington Statue group’s rededication on 18 June last year.
The latest capsule contains soil from Sulgrave Manor, the Washington ancestral home in England, mirroring soil donated by Mount Vernon for the capsule in Trafalgar Square.
In a statement, Lammy said: ‘Time capsules are about speaking to the future. I am confident that when this treasure is opened up by our descendants, they will find Britain and America still the closest of friends and the surest of allies.
‘Two free, multiracial, English-speaking peoples anchoring our great Western family. This is who we are: a family based on freedom, a family that never tires in its pursuit of greatness and new horizons.’
George Washington Memorial unveiling in 2025