Post Office Rifles Recognition patch

[matfowler]

Hi all, I am researching a British uniform worn in the Great War by 8th (City of London) Battalion (Post Office Rifles) 2nd London Regiment. I have the cap badge and metal shoulder title badge, and reproduction "2nd P.O.R." shoulder title patch made from an IWM reference, but do not know what tactical recognition patch would have been worn on the sleeves? I have seen an odd references to a red square, and a blue/red/blue horizontally striped square, but not any conclusive information.
Can anyone enlighten me how these recognition patches worked? Was it by your job, regiment, battalion, geographic area? When were they used - all the time, or just in certain offensives?
Any help much appreciated.

[Bill A]

Hello matfowler, welcome to the Forum. Your account is active and open for responses.

[Drew]

Hello there,

Not sure if you will get this now, but just wanted to say that the 2/8th Londons would have worn a "dark blue horizontal rectangle" patch. Information from the IWM.

Interested to hear about your other references to a different type of patch. Would you be able to add anything?

Regards,

Chris