You are strolling through Sheffield city centre, the clock strikes 1pm and all of a sudden, the air is filled with a piercing, screeching siren.
Chances are that at one time or another, especially if you are a newcomer to Sheffield, you will have been startled or left puzzling what the siren in blaring out near to Barker's Pool is actually for.
Well, if you look above the entrance to jewellery store HL Brown, there's a clue - and what's more, it has been a tradition for 143 years.
Above the entrance, there's a small black and white sign proclaiming "1 o'clock time signal" and alongside it, the siren that you hear each and every day.
The signal – although not necessarily in the form of a siren - has been a feature of city life since at least 1874, when clocks and watches were less reliable than they are today and when the time they showed could vary by as much as 30 minutes across the country.
HL Brown’s time signal was linked directly to Greenwich, home to one of the first public time signals – originally intended for ships on the Thames.
The signal was relayed to HL Brown in Sheffield for the first time by the miracle of the telegraph, so that the company could ensure the clock it used to set customers’ timepieces by was set to Greenwich Mean Time and the people of Sheffield could set their watches.
The link to Greenwich is no longer necessary to keep the siren sounding as regular – or maybe more regular - as clockwork at 1pm.