Harare - Zimbabwe's finance minister Patrick Chinamasa had to be shielded from protesters by British police as he left a meeting in London - on the same day that riot police in Harare were busy attacking angry protesters.As footage of police brutality towards residents of Epworth suburb sparked outrage on social media, another vastly different video clip emerged: a firm, courteous human chain of British police officers apparently providing a safe exit from Chatham House to Chinamasa, who is in the British capital in a desperate attempt to get support for Zimbabwe's proposal to have its international debt arrears cleared.The video, posted by well-known activists' group Restoration of Human Rights in Zimbabwe shows a sleek black limousine identified as belonging to the Zimbabwe ambassador in London idling while a small number of protesters wait outside Chatham House, the headquarters of the think-tank. Police officers form a chain across the pavement, separating the protesters from the entrance to the building. The video has already had more than 45 000 views.Watch the video here."It became apparent that Chinamasa and his companions were afraid to come out and face the music," said the UK-based Zimbabwe Vigil, whose members also took part in the protest."Eventually the police arrived and provided a safe corridor for Chinamasa and his friends to access the Zimbabwean Ambassador’s car amid jeers from protesters, fired up by messages from home of mounting unrest in all urban areas," the group added in a statement.State radio in Zimbabwe says 57 people were arrested in the wake of Monday's clashes between police and commuter omnibus drivers and touts. In an ominous warning, Zimbabwe's pro-Mugabe police force said it would "severely deal" with "all those inciting and engaging in violence" ahead of a strike by civil servants on Tuesday and mounting calls for a nationwide shutdown on Wednesday.Tensions are rising in Zimbabwe over cash shortages, the high number of traffic police demanding cash from road-users, and new controls on the import of basic goods which will put many informal traders out of work.As Chinamasa appeared on the BBC's HardTalk programme on Tuesday morning, Zimbabwean @MariaZest1 tweeted: "Chinamasa is gonna have a heart attack. Defending his corrupt government."