If you're in the vicinity of the road called London Wall (where the car park referenced in the article is) then it's only a short walk to London's Roman amphitheatre [1]. It doesn't seem to be very well known but is quite impressive. It's one of very many bits of Roman history entombed in basements of London buildings.
The Merrill Lynch Financial Centre also has a big chunk of Roman stuff in the basement - but there's no public access and no access to the walkway around the ruins even if you're an employee.
The Merrill Lynch Financial Centre also has a big chunk of Roman stuff in the basement - but there's no public access and no access to the walkway around the ruins even if you're an employee.
[1] https://www.thecityofldn.com/directory/londons-roman-amphith...