A GCHQ spokesman said some of their most talented code-breakers were affected: ‘They are very creative but may need support, including adjustments in the workplace, such as IT tools and computer software, or [reductions] in their working hours.’

In a speech last year, Sir Iain Lobban, the director of GCHQ, said: ‘Part of my job is to attract the very best people and harness their talents, and not allow preconceptions and stereotypes to stifle innovation and agility.’

Adrian Culley, a cyber expert and former Scotland Yard computer crime detective, said: ‘Dyslexic people have the ability of seeing codes with patterns, repetitions and omissions.

‘Dyslexia may in other circumstances be regarded as negative – but most people only get to see the full jigsaw picture when it’s nearly finished while dyslexic cryptographists can see what the jigsaw puzzle looks like with just two pieces.’