By Andrew MacAskill NEW DELHI (Reuters) – A small number of Ukrainian troops are being trained in Britain for the first time since the start of the Russian invasion as Prime Minister Boris Johnson steps up his military support to help Ukraine fight off its neighbour.The troops began training with armoured patrol vehicles donated by Britain this month, Johnson’s spokesman said. Britain is providing Ukraine with 120 armoured patrol vehicles, including the Mastiff, which can be used as a reconnaissance or patrol vehicle.The spokesman said Britain, in conjunction with its allies, was providing new…