Swans are seen in a lake in London May 16, 2020, the first weekend after British Prime Minister Boris Johnson unveiled a lockdown exit roadmap on May 10. (Xinhua/Han Yan)

People walk past a lake in a park in London May 16, 2020, the first weekend after British Prime Minister Boris Johnson unveiled a lockdown exit roadmap on May 10. (Xinhua/Han Yan)

Tables of a restaurant are piled up in a park in London May 16, 2020, the first weekend after British Prime Minister Boris Johnson unveiled a lockdown exit roadmap on May 10. (Xinhua/Han Yan)

People exercise in a park in London May 16, 2020, the first weekend after British Prime Minister Boris Johnson unveiled a lockdown exit roadmap on May 10. (Xinhua/Han Yan)