“We are aware of a cybersecurity incident involving Transport for London, and are working closely with the National Cyber Security Centre and with TfL itself to respond to it.

”William Wright, chief executive of cybersecurity company Closed Door Security, said: “The big question people will also want to know is who carried out the attack and if it can be attributed to another country, like Russia.

TfL was also attacked by Russia last year, so it definitely isn’t out of the realms of possibility.

Furthermore, given Russia’s recent uptick in attacks on the West, it wouldn’t be surprising, but it is far too early to speculate.

”TfL was targeted by Russian hackers in June last year as part of a wider raid that saw personal information stolen.

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