Britain\'s public finances showed their biggest surplus for four years in January, boosted by higher tax revenues and by government austerity measures official data showed on Tuesday. The public sector net borrowing measure registered a surplus of £7.8 billion (9.3 billion euros, $12.3 billion) last month, the Office for National Statistics said in a statement. That was the biggest surplus since January 2008 and compared with a surplus of £5.2 billion in January 2011. Market expectations had been for a surplus of £6.4 billion according to analysts polled by Dow Jones Newswires. Britain\'s public finances usually log a surplus in January because they are lifted by annual taxation receipts. \"The public finances saw clear improvement in the key month of January compared to a year earlier which adds to the recent better news of the economy,\" said IHS Global Insight economist Howard Archer.