HM Treasury are launching a new 12-sided one pound coin on 28th March 2017 Credit:Kindred Agency Tesco’s shopping trolleys are to be left unlocked across scores of its stores as the supermarket giant performs upgrades for the new £1 coin after it enters circulation.The new 12-sided coin enters circulation on Tuesday, and there will be a transition period of just over six months when the old “round pound” is still accepted as legal tender.Consumers may be left rifling through their wallets for old round pounds, as some coin-operated machines will not immediately accept the new £1 coin.A Tesco spokesman said trolleys across “fewer than 200” of its stores will be unlocked from Tuesday as the store upgrades them to accept the new coin. He said they will all be upgraded by the time the new round pound ceases to be legal tender on October 15.The spokesman said: “We’re replacing the locks on our trolleys to accept old and new pound coins as well as existing trolley tokens.”As an interim measure we will unlock trolleys while this process is completed and we will continue to have colleagues on hand to attend trolleys in our stores, so our customers aren’t affected by the changes.”According to the Automatic Vending Association (AVA), around 15% of vending machines will not immediately be able to accept the new £1 coin on Tuesday.The AVA said that with around half a million vending machines across the UK, ensuring all of them are upgraded is a “major operation”. The body has estimated that all vending machines will be fully upgraded by the end of the transition period on October 15. Jonathan Hart, chief executive of the AVA, said the upgrades needed for the new £1 coin will cost the vending industry an estimated £32 million.He said: “We support the Royal Mint and the Treasury’s actions to protect the integrity of currency in the UK and reduce the level of fake coins in operation.”A spokesman for the British Parking Association said the majority of parking machines will be ready on time but some will still need to be upgraded. Some older machines may not be able to be upgraded and may need to be replaced.A statement from the association said: “This is a huge programme of work and the Royal Mint recognises this with the planned six-month co-circulation period, at the end of which all coin-handling equipment should be ready to accept the new £1 coin.”The new coin has been described as the most secure coin in the world. It boasts high-tech features, including a hologram.The coins have been made at the Royal Mint in Llantrisant, South Wales, at a rate of three million per day.They have a gold-coloured outer ring and a silver-coloured inner ring and are based on the design of the old 12-sided threepenny bit, which went out of circulation in 1971.It might take a few days or weeks for people to start seeing the new £1 coins turn up in their change as they gradually filter into general use.The production of the new coins follows concerns about round pounds being vulnerable to sophisticated counterfeiters. Around one in every 30 £1 coins in people’s change in recent years has been fake. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.