Salisbury nerve agent attack: How might Britain respond?

Theresa May said Britain will deploy the "full range of tools" from across the National Security apparatus to counter the threat posed by the GRU, Russia's military intelligence service.

While some measures that could form part of the response are likely to be played out on the world stage, others will take place under the radar.

-Cyber

Speculation about the possibility of a retaliatory cyber strike emerged in the wake of the Salisbury poisoning in March, and again after police identified two Russian nationals as suspects. The Times reported that such operations will aim to disrupt the GRU by scrambling communications and obstructing access to finance. Britain's capacity in the area of "offensive cyber" was summarised in December by the Commons Intelligence and Security Committee, which has access to high-level security figures and highly classified material. Offensive cyber covers a range of measures including possible retaliation and capabilities to attack wider systems or infrastructure, according to the committee's annual report.

-Counter-espionage

Britain's security chiefs were flagging up the threat from Russia prior to the Salisbury attack. In a speech in October last year, MI5 director general Andrew Parker referenced the agency's work "against espionage and other clandestine activity by Russia and other foreign states who seek to do Britain harm". Methods adopted could include alerting someone to a foreign intelligence service's interest in recruiting them or providing advice to companies with sought-after information. Security agencies could also seek the expulsion of foreign intelligence officers if their activity is deemed to be especially intrusive or threatens real damage to UK interests.

-New border powers

The disclosure that the two Salisbury suspects flew in from Moscow two days before the poisoning bolsters the Government's case for new measures to stop spies and agents at the border. Under plans unveiled earlier this year, police and immigration authorities will be handed anti-terror style powers to intercept individuals to determine whether they are or have been engaged in "hostile activity".

-International pressure

Britain will continue efforts to rally the international community and close partners to strengthen defences against and clamp down on malign Russian activity. In the aftermath of Salisbury, Britain, Nato and 28 other countries expelled more than 150 Russian intelligence officers in the largest collective expulsion ever.

-Diplomacy

While she made clear the UK's outrage over the attack, Mrs May did also commit to continuing to engage Russia "on topics of international peace and security". She said: "We continue to hold out hope that we will one day once again enjoy a strong partnership with the Government of this great nation."