Leading article: A salutary wake-up call about sleepers

The detention and likely deportation of a young Russian who worked as an MP's assistant make for a tantalising story that reinforces many stereotypes. Coming so soon after the unmasking of a network of Russian sleepers in the United States, it is bound to raise the spectre, justifiably or not, of Britain being similarly targeted. Not that the British security services have been under many illusions about the potential value to the Kremlin of the large Russian presence in the UK. Indeed, it would be more surprising if security services, theirs and ours, were not seeking to exploit this for their own advantage.

Of course, a murkiness attends anything that touches the world of intelligence. Charges and counter-charges are diabolically hard to prove. The response of the Home Office yesterday was its standard refusal to comment "on individual cases". Someone somewhere, though, was clearly keen that the information should come out – someone, it might reasonably be speculated, not a million miles from MI5. If you ask whose interest this serves, the answer is clearly that of British intelligence: it shows that its agents are ever-vigilant and the publicity could deter others.

Whatever the rights and wrongs, however, the case of Katia Zatuliveter is bound to raise concern. How was it that Mike Hancock – who is not just any MP, but someone representing a major Naval port and a member of the Commons defence select committee – came to recruit a Russian aide, even if she does have a British Masters degree? Many people may be surprised that foreign citizenship was no disqualification for such a job.

For the concern should not be uniquely about Russia. There are many countries whose interests may well differ from ours, and which might like to infiltrate the corridors of power. Is it known, for instance, how many other non-British nationals work for MPs, and so obtain Commons passes? How are they recruited? How are they vetted? The shadow Foreign Secretary, Yvette Cooper, raised the matter of vetting and parliamentary security when she commented on the case yesterday. The Government should be asking the same questions.