The US president refused to visit the new embassy in July, saying it was in an ‘off location’

The new US embassy in London has been famously derided by Donald Trump, who was so unimpressed with its unfashionable location and the “bad deal” behind it he refused to attend its opening ceremony.

But the US president’s lack of enthusiasm for his country’s new home in the capital has not put off visitors to the fortress-like building, a select 75 of whom will breach its moat and 6in-thick bomb-proof glass on Saturday as part of the annual Open House London festival.

In a late-night tweet in January, Trump declared he was so unimpressed with his embassy’s move from Grosvenor Square in Mayfair to the “off location” of Nine Elms, Wandsworth, that he had cancelled his trip to the UK.

Donald J. Trump (@realDonaldTrump) Reason I canceled my trip to London is that I am not a big fan of the Obama Administration having sold perhaps the best located and finest embassy in London for “peanuts,” only to build a new one in an off location for 1.2 billion dollars. Bad deal. Wanted me to cut ribbon-NO!

London’s new US embassy: a very diplomatic America on Thames Read more

He later called the south London site “lousy” and “horrible” and blamed his predecessor, Barack Obama, though the US confirmed the deal had been signed off under the George W Bush administration. The trip went ahead in July, with the president snubbing the £800m embassy.

Those visitors who managed to snap up tickets will be able to tour the lobby, exhibition space and gallery of a building that the Observer called “as nice a fortress as possible” and “better than everything else that developers are putting up around it”. Fittingly, however, guests have been warned to expect “airport-style security” in order to enter.

The world’s most expensive embassy is the most eye-catching new addition to the festival’s roster of 800 buildings welcoming an expected 250,000 visitors. Other sites include the newly renovated Royal Opera House, the Here East technology campus in what was once the London Olympics 2012 media centre, and a “sustainable” riverside housing development in Barking, east London.

Diplomacy aficionados who cannot make it past US security might wish to try their luck at the embassies of Estonia, Poland, Slovakia and Hungary, all of which will also open their doors.