Unfortunately the answer is yes, although many if not most people do not. So you probably think its just a sales pitch from your locksmith when he tells you that the average amount of key sets in existence to UK properties is 5…erhh…yes 5! So have you got them all? Of course its mostly innocent ie people who sell simply dispose of their keys as they move on, or have left them with a trusted trade or friend who forget about them or do the same. But as a real life & real time working example listen to this, just this week I passed on a job to a colleague in the Ludlow area for a couple who had just bought a property in the Clee Hill area. The very nice couple had been living in Greece for their retirement and for obvious reasons were moving back to the UK. They purchased the property from a reputable estate agents and 2 weeks ago visited the property to move in their first load of belongings. All went well, a lovely property in a very nice area, lovely views across the hills and a highly visible secure access to all the property fronts. They returned the following week to find the property had been entered with no evidence of forced entry and ok so only some minor belongings had been moved or taken but who ever it was helped themselves to refreshments and took a shower! It is a risk that does exist and it is your choice to spend a relatively small amount of money to change your external door locks.