British Prime Minister Theresa May greeted a member of the public in Salisbury by knocking fists in an unusually casual manner for a politician.
May, who Thursday visited the English cathedral city, also posed for photographs while fist bumping.
She had visited the scene where Russian former double agent Sergei Skripal and his daughter were found unconscious on a bench after being poisoned with a nerve agent, meeting with businesses and emergency services.
Skripal, 66, and his daughter Yulia, 33 were found outside a shopping centre in the centre of the city on March 4 after being exposed to what the British authorities have identified as a military-grade, Soviet-era Novichok nerve agent, that hadn't been used in Europe since WWII, according to a joint statement released by France, Germany, Britain and US.
The pair remains critically ill in hospital.