LONDON (Reuters) - British police started to reopen roads around Buckingham Palace in London late on Thursday after investigating a suspicious vehicle.  All road closures are now in the process of being removed,  London s transport authority said.  There s significant congestion in the area but this should now improve.  A police spokesman said road closures were being lifted. Queen Elizabeth is not at Buckingham Palace as she travelled to her Sandringham estate in eastern England earlier on Thursday for the Christmas holiday. 