The secret of how to make puppies well-behaved has finally been found, and it involves stroking them with a toothbrush and exposing them to men with moustaches.

The charity Guide Dogs, which trains 1,300 puppies a year, has created the first programme which is scientifically proven to have a long-term, positive impact on a dog’s behaviour.

Key to its success is allowing puppies to experience as many new environments and people as possible within their first six weeks of life so they are not startled, excited or scared by the strangers, or odd scenarios, when they venture outside.

Puppies are born blind and deaf, so the first two weeks of the programme centre on touch. Handlers offer comforting strokes, cuddles and comb their fur with a soft toothbrush to help them to bond with humans.