The search for a person within The National Archives can sometimes yield a line or two about who they were and what they did, but for me, the enduring appeal of the MI5 files at Kew is the astonishing level of detail you can often glean from a Security Service report.
Files in the KV 2 series in particular, labelled Personal Files (PF) at the Security Service, can provide a lot more colour than most official sources, containing everything from transcripts of phone conversations, to intercepted letters and photographs.
Few people in the latest batch of Security Service files have a reputation as unsavoury as that of Ivan Serov. If you can tell a lot about somebody from the company they keep, this ‘devoted friend’ of Stalin and trusted lieutenant of Beria was clearly a man best avoided.
He was responsible for supervising – in the euphemistic language of the time – the ‘mass deportation’ and ‘purging’ of anti-Soviet elements across the Baltic States, Ukraine and Poland as a result of which many hundreds of thousands were killed.