The national chain, which has stores across Yorkshire and employs more than 1,200 people in the region, was ranked among the best performing retail betting outlets in undercover tests by independent ID check auditor Serve Legal.
Testers aged 18 and 19 visited stores to monitor ID challenges. Staff approached testers in 86 per cent of visits across the UK; in Yorkshire, this climbed to 87.1 per cent.
This compares to 82 per cent for bookmakers in general.
The results come weeks after the UK Gambling Commission warned that more must be done to prevent underage gambling.
Andrew Lyman, head of public affairs and UK compliance, said the bookmaker was “delighted” by the outcome of the results, but “we will not be sitting back and resting on our laurels”.
He added: “The staff in Yorkshire are doing a very effective job in identifying possible underage visitors to our shops.”
William Hill employs two measures of success in age checks: overall challenge rate, and challenge on entry. Mr Lyman said its overall challenge rate is now “at least equal” to supermarkets and convenience stores.
“We are now focussed on driving up the challenge on entry rate because we recognise the imperative of challenging straight away any young person who enters a betting shop before they can attempt to gamble,” he said.
Matt Eastwood, commercial manager at Serve Legal, said William Hill’s national results are now on a par with supermarkets and convenience stores, which have traditionally performed well as restricted age sectors due to long-standing checks from trading standards and police.
He said: “The bookmaking sector has raised the bar significantly and improved performance in the past five years – in 2009 it was 50 per cent ID check rate. William Hill has improved every year and is a good example of how seriously the sector is taking this subject.”
Sonia Wasowska, compliance manager at William Hill, said the bookmaker adopted a ‘Think 21’ approach in 2007, meaning any customers who a member of staff thinks may be under 21 should be challenged for ID.
Shop teams are trained on the policy throughout their career, she said.
Ms Wasowska said: “Their training starts during a two-day off-site induction and continues during their off-site training days within the first six months, and individual training in shops with their line managers.
“The policy is re-enforced during the quarterly compliance distance learning and emphasised regularly by the operations teams to all William Hill employees.
“We constantly emphasise the importance of challenging young-looking individuals for ID on entry to our shop teams. Their training, operations management support and the general company focus on getting it right is demonstrated in our figures.”
She added: “We practice an individual approach towards monitoring individual shop results and continuously assess what more can be done to improve.”
While William Hill “does not consider underage gambling to be a problem”, the Gambling Commission has continually expressed concerns over controls to restrict access to youngsters.
In September, it warned many operators continue to have “inadequate controls for preventing underage gambling”.
Local authorities can revoke licenses for gambling outlets that repeatedly fail test purchasing, it added.