I wrote to Canadian Embassy in Riyadh asking for PCC request letter. Their reply, received the same day, was:
"Dear Madam/Sir,
"In order to assist you with your required Police Clearance Certificate, please send your Immigration file number. Police Clearances only have one year validity.
"If you are applying from London or Abu Dhabi no assistance will be provided and you will need to contact your Immigration Office."
I wrote to London Visa Office, they replied the next day:
"Dear Applicant,
"Thank you for your message. The Arabic request letters to obtain police certificates from Saudi Arabia have been sent to your representative's mailing address by TCS courier service.
"Yours sincerely,"