By David Milliken LONDON (Reuters) – Britain’s government must focus on sound public finances and avoid further fuelling inflation by pumping up demand, new finance minister Nadhim Zahawi is due to say in his first major speech on Tuesday. Zahawi will address the City of London’s annual Mansion House dinner, where he is set to confirm a post-Brexit reworking of financial regulation inherited from the European Union, including Solvency II insurance rules. However, tackling inflation is a top priority alongside boosting longer-term growth, according to speech extracts provided ahead of the event…