Darkness, fire and screams: Kiev's gun battles have horrified Britain. But one of the most sinister - and important - scenes of Ukraine's political violence took place much closer to home, in usually-peaceful Knightsbridge.

Chanting 'shame on you', more than 150 protestors crammed onto a cold London pavement. But they had not chosen either the Ukrainian embassy or the Houses of Parliament to demonstrate. They were protesting outside Number One Hyde Park. As they shouted, the Ukrainian protestors craned their heads upwards to the metallic balconies of this hulking icon of a new London. London buses, not Berkut troopers, hummed passed. Then began the singing for the dead.

To the British, Number One Hyde Park is a symbol of what David Cameron as prime minister and Boris Johnson as mayor envisage for London. This glinting billion-pound development was built to reel in foreign billionaires.

To the Ukrainian demonstrators below, Number One Hyde Park is a symbol of impunity. The protestors were not calling out to the ether. They were shouting up to the apartment of the Ukrainian oligarch Rinat Akhmetov.

This man is worth more than $15 billion. But calling him an oligarch misses the point. He is also a political boss. Akhmetov controls more than 50 lawmakers from the governing party - the Party of Regions - whose leader Viktor Yanukovych is responsible for more than 100 deaths in downtown Kiev.

Akhmetov is only the best known of the Ukrainian politicians with British residency. He is only one of the Yanukovych-loyal billionaires to have a London address. Ukrainian government contracts have enriched these men, which is why they want to keep the Yanukovych government going.

The protestors also cried 'criminal elite'. The Ukrainian establishment, like the Russian establishment, has moved its fortunes, wives and children offshore. The entire elite has money in the EU: from powerful ministers to pliant spy chiefs, from provincial governors to heads of the military police.

Moving between the protestors - young and old, nationalist and democrat - I try to make sense of what they thought of Britain. The answer is not pretty.

On the topic of the UK, those protesting at Number One Hyde Park think exactly like those protesting in Kiev and Moscow. They think it is hypocritical for Britain to speak out against corruption when trillions of dollars of corrupt pillage find safe harbour in British tax havens and London's property market. Pillage, not Putin, is the reason Yanukovych has ordered his security forces to shoot in Kiev. There is nothing idealistic about the Ukrainian president; there are no romantic notions of Russia in his government.

The figures speak for themselves. The president's son, Oleksandr Yanukovych, has seen his wealth increase by well over 7,000 per cent since his father took office. He is now worth more than $510 million. Like any Ukrainian with money, he operates through foreign holding companies based in the British Virgin Islands, Switzerland and the Netherlands.

Ukraine's elite would never dream of hiding their wealth in Russia. They have it hidden in Britain, its tax havens, and elsewhere in the European Union. Forced to choose between London security and backing Kiev bloodshed, they go for Number One Hyde Park. But this makes them extremely vulnerable, should London and Brussels ever decide to visa-ban them or block their banking activities on account of politics back home.

The Knightsbridge protest is part of something bigger. Russian and Ukrainian activists have been campaigning non-stop for the UK to stop making it so easy for criminal officials to hold their assets in London. The fact that nothing has been done means Britain is now seen not only as cynical but as complicit in their plunder of Ukraine.

'Britain is open for business.' This is a nice slogan. But when in practice it means that Ukrainian political bosses and police chiefs with blood on their hands can safely hide stolen assets in the UK the globalisation glitz turns an ugly color.

The Conservative party will not review its vision for London as a no-questions-asked destination for foreign capital. This is evident in its response to the city's housing bubble and in its refusal to listen to Russian and Ukrainian pleas to restrict UK access to criminals.

The Labour party needs to acknowledge what David Cameron and Boris Johnson cannot: that turning London into a free-trade zone for mafia-politicians makes a mockery of Britain's mission to fight for human rights around the world. Then it needs to restart its debate on foreign policy. It should publically challenge the hypocritical gap in our rhetoric - damning corruption while accepting the proceeds of corruption - and put forward a new UK visa policy that blocks human rights abusers from entering the country and using our banking system.

The policy answer might look something like this. Labour should propose that Britain - along with any other EU state willing to ally itself with us - will sponsor an independent commission of senior former judges, which would make annual recommendations to the European council on who should be barred from entry on grounds of rights violations. The council already has the power to decide who may or may not enter its territory, so no new EU legislation is needed.

This must happen on a European level. Labour should propose that this policy be adopted by the party of European socialists in the upcoming European elections, as a progressive answer to a morally corrosive issue.

Darkness, fire and screams: Kiev has turned into a nightmare. Doing nothing now to begin restricting the access of mafia-politicians to their fortunes sends a hideous signal: that Britain is open for business.