Condensation and water mark on wall underneath windowsill

[SG82]

Dear All,

Just noticed today quite a lot of condensation and water marks underneath the windowsill beneath 2 windows in my flat.

There was some condensation on the windows and some of the top of the sill but am more worried about the condensation occurring on the wall underneath the windowsill.

Any help would be much appreciated.

 

[foxhole]

Likely just condensation running off window , then off sill, need ventilation.