By Jack Stubbs and Brian Love LONDON/PARIS (Reuters) – Commuters faced a day of traffic chaos in London, Berlin, Paris and Madrid on Wednesday as taxi drivers mounted one of the biggest protests against Uber, a U.S. car service which allows people to summon rides at the touch of a button. In London, up to 12,000 taxi drivers plan to tie up the streets around Trafalgar Square, just a stones throw from Prime Minister David Camerons official residence, from 2 p.m. (1300 GMT). Taxi drivers across Europe say applications of companies like San Francisco-based Uber Technologies Inc. are breaking local taxi rules across the European Union and threatening their livelihoods.