Fallout from the Salisbury attack has continued this week, as the war of words between London and Moscow shows no sign of abating. Yulia Skripal, the daughter of spy Sergey Skirpal, who was the victim of a nerve agent attack along with her father last month, has been released from hospital this week, leading to the Russian embassy to demand assurances that she was not being held against her will by British authorities, sparking an angry backlash from the government. Her father, the assumed target of the attack, is recovering well in hospital after several weeks in critical condition, and is expected to be released within a few weeks.

This latest spat comes amidst rising international pressure from the British allies on Russia, following allegations from a variety of British sources, including Prime Minister Theresa May and Foreign Secretary Boris Johnson, that the Kremlin ordered an attack on Sergei Skripal. Such an attack, on British soil and affecting British citizens, would be a considerable breach of international law, and the allegation has led to a number of joint responses from Western nations, culminating in the mass expulsion of Russian diplomatic staff from the USA, Canada, Australia, and an array of European Union nations. Russia has indicated that it will respond in kind.

The Kremlin has consistently denied that it was behind the attempted assassination of Skripal, placing it at odds with British intelligence. Russian spokespeople have suggested the British may have carried out the attack themselves, and questioned the validity of any tests to establish the origins of the agent used in the attack. Much of the debate has focused on the use of Novichuk in the attack, a chemical agent that has only ever been known to be produced in Russia. Porton Down, the Ministry of Defence’s chemical agent laboratory, said last week that it was unable to identify the specific location of the chemical used in the attack on the Skripals’; however, intelligence sources have identified is as coming from within Russia, according to the Prime Minister’s statement to the House of Commons.

The attack on Sergei Skripal is the latest in a series of a suspicious deaths of Russian nationals on British soil, the most famous being the murder of Alexander Litvinenko with plutonium in a London restaurant in 2006, which was eventually traced back to Russian agents. Skripal was a former Russian spy, who turned double agent and spied for the British. He was tried and convicted in Moscow, and eventually sent to Britain as part of a spy swap in 2012. The attempted assassination comes amidst the re-election for Vladimir Putin.

The election occurred in disputed circumstances, with prominent rivals banned from challenging the incumbent, and opposition media outlets often forced out of covering the election. Mr Putin faced no significant opposition, and his democratic credentials have weakened since he first became President in 2000. The Russian leader notoriously has little time for dissidents.

Despite Russian denials, the international community accepted British evidence that the source of the attack was the Kremlin and responded accordingly.

The backdrop to the diplomatic expulsions is a worsening of ties between Russia and the West, fuelled by Crimea crisis, stalemate over Syria and the future of Bashar Al-Assad, and the accusations that Russian hackers interfered in the 2016 Presidential election. The Salisbury attack furthers this tension between the old foes.