The opening part of a Bellingcat investigation into the private operator of UK and other nation's visa issuing being subverted by the Russians, hence the two Skirpal suspects having visas for year to enter the UK and other European nations. It starts with:
One of the unanswered questions lingering after Bellingcat’s unmasking of the identities of suspects in the botched-up poisoning of Sergey and Yulia Skripal, is how two (or, likely, more) undercover GRU officers were able to obtain visas to travel to the UK. Securing a visa to the UK – as to most of EU destinations – is not a trivial procedure. A single-entry visitor visa is relatively straightforward to procure – it requires either an invitation from a UK resident or business, or a pre-arranged tourist trip.
Link:https://www.bellingcat.com/news/uk-a...l-visa-system/