Gaps around exterior of old Victorian sash windows. Fill or not?

[gbyng]

I noticed when painting the frames of the original sash windows that there are gaps around the outside of the frames (between the frame and the external brickwork).
The gaps are only 2-3mm and don't let in any draught or wet.
My first instinct was to run some kind of filler around but then I wondered if the gaps are there for a reason? Maybe to help any water that might get into the frame to dry up before it rots the timber?
I've heard of weep holes before but I'm not sure if it's the same thing.

 

[blup]

You can apply external frame sealant, one thats overpaintable. The gap is from thermal movement between the different materials.

Blup

 

[gbyng]

You can apply external frame sealant, one thats overpaintable. The gap is from thermal movement between the different materials.

Blup

Thanks Blup. Does it not need to be breathable though?
I stumbled across this - they recommend to use oakum

Heritage House | Sealing around windows and doors

Old houses have a multitude of window and door types. We have one overarching piece of advice for anyone with an old house. External joinery will only deteriorate if it gets wet. And stays wet. Windows and doors can last for hundreds of years if they can breathe, and moisture isn't trapped...

www.heritage-house.org