The new postboxes are being rolled out over the next few months with Royal Mail hoping it will help shore up its share of the market.

"Our message is clear, if you have a Royal Mail label on your parcel, and it fits, put it in a postbox and we'll do the rest," Mr Clarkson said.

But it may not be enough to prevent rivals like Evri and Yodel, who often offer cheaper delivery, eating further into its business.

Online communication, combined with more competition in the delivery business, has already caused its first casualty among traditional postal services: Denmark recently ended its letter deliveries service, PostNord.

Royal Mail recently said it will start to deliver second-class letters on every other weekday and not on Saturdays to help cut costs.