Scottish cavalry men - Unknown unit / 1910s-1920s

[Lemataf]

Hi,

here is a picture I have since a while already, from an unknown unit. Apparently showing men from a scottish cavalry unit, I would say in the years 1910s to 1920s.
Completetely here outside of my usual themes, hence asking please for your help to try identifying this unit & time period.
Worth to mention that this is the first time I see a pic with british soldiers wearing an apparently cut down tartan trouser, used as a short.
Maybe the unit patch on the tropical helmet can help?

Any information to help id this unit, time period (& place where possibly taken) most welcome.

Thanks & Best Regards,

Jean-Daniel