I would imagine so in an emergency, but often in older properties a stop tap would isolate the supply to several other houses so turning yours off may also turn off your neighbours water.
While there are plenty of web references (including Youtube videos about operating external stopcocks) which state that householders aren't officially allowed to turn the water supply to their property on or off externally, the water supply companies actually seem happy enough to allow people to do so.
I suggest finding the external stop tap to see which type it is, Bazile. (i.e. actually try turning it off). There are different types, with some just requiring a quarter turn to stop the flow of water and others needing several full turns (like a sink tap). Some are fairly easy to operate by hand but others require the same type of hydrant key which the fire service use. (There are other types too).
This video initially shows the operation of a 'hydrant-style' stop tap but then shows how much easier it is to get to the stop tap next to a water meter. (Even so, the stop tap shown there is different to the one next to my own water meter):