“The judge who had heard a substantive application would almost always be the right judge to deal with consequential issues as to costs, even if he had made findings adverse to a party in the course of reaching his conclusion. However, exceptional circumstances might arise where there was apparent bias stemming from the facts of the case which meant that the judge should have recused himself from dealing with the issue of costs.”
WLR Daily, 14th August 2013
Source: www.iclr.co.uk