Days before my lunch with Sir Jeremy Fleming, an email lands in my inbox, asking for my food order. Then I am told to be at the exit door of London’s Science Museum at the unfashionable time of 11.30am. The UK’s cyber intelligence chief has only days left in the job and is still not leaving anything to chance. The chosen entrance to the museum avoids the crowds of children on school trips; the second-floor café is open on that day only for us, thus the need for a pre-order. 

The choice of venue is a deliberate one, placing GCHQ, the signals intelligence agency, in the context of Britain’s broader scientific achievements. The museum is where GCHQ celebrated its 100-year anniversary in 2019, with an exhibition that traced its history of code-breaking from Bletchley Park to today’s cyber activities.

Before we head up to the restaurant, we take a whistle-stop tour of the museum’s display of early precision and measurement tools made in London in the 18th century, clearly one of Fleming’s favourite spots. As he scrutinises the instruments, he tells me about the agency’s “poachers and gamekeepers”, the pure mathematicians who protect secrets and break codes. “We have the largest number of pure mathematicians in the UK,” he says proudly.