The “barrage” of betting advertisements around Boxing Day sporting fixtures will exacerbate Britain’s growing gambling problem, NHS bosses are warning. Promotional techniques by unscrupulous betting firms, including free Christmas bets, will increase gambling-related harm by encouraging punters to wager sums they cannot afford, they say. Gambling addiction is causing so much damage that the NHS in England has almost doubled from eight to 15 in the last year the number of specialist clinics it runs to help addicts, it said. The health service is facing “an uphill battle” to provide enough care to the increasing number of people whom GPs