May I suggest (subject to expert legal opinion)that if a foreign national's first language is not English, the UK Police are likely to cover themselves by providing an interpreter to avoid confusion and jeopardise the interview/case. The Russian Embassy may require an accredited translator to be present.
A journo may abbreviate this explanation to 'the suspect could not speak English'
We have all heard ATC traffic (Universal language - English) with foreign pilots or tried to communicate with our local bank via a call centre in India!
Kick the tires(location UK)are you English UK or English US? It may be critical when checking fuel load in gallons.
Your immediate readback of G-STAWs post was inaccurate '..so a(n) interpreter..' but I bough to your communication skills.