I don’t think that’s true about only Royal Mail can post there. There’s clear instructions on gov.uk for all couriers on where to send the mail if they come acr

I don’t think that’s true about only Royal Mail can post there. There’s clear instructions on gov.uk for all couriers on where to send the mail if they come across this post code, it’s not some weird secret. https://www.gov.uk/government/organisations/hm-revenue-customs/contact/couriers https://www.gov.uk/government/organisations/hm-revenue-custo...