The man who knocked the formality out of the suit reveals the rules that have made him the godfather of British menswear.

When it comes to British menswear, Sir Paul Smith is the archetype for every tailor who dreams of becoming a global brand. He invented the much-borrowed phrase “classic with a twist” and has built his brand around providing precisely that.

He has described his style as “Savile Row meets Mr Bean” – that is, a love of tradition with a sense of humour. The playfulness comes through in various ways: some colourful stitching, deliberately mismatched buttons or hidden patterns. Linings contain in-jokes between him and his customer. These partially hidden extras allow men who are obliged to dress formally to show a little individuality.

The Paul Smith empire has grown slowly but steadily over the past 44 years. He’s now a knight of the British Empire estimated by the Sunday Times Rich List to be worth £280m – but he’s never forgotten his humble Nottingham roots having started out in 1970 with a 12sqft windowless shop. Sir Paul has never borrowed money and every one of his 200 stores globally is very different and designed in-house.

Even at the age of 68, Sir Paul remains chairman and chief designer of his brand. He designs everywhere and is never without a Rhodia notepad and a pencil. A keen photographer, he also shoots most of his own advertising campaigns. As a result, the global company manages to retain a family-run personal touch often lost in organisations of similar size.

Each day begins the same way. He swims at The Royal Automobile Club in Pall Mall before meeting his friends at a café on Old Compton Street in Soho for a breakfast of coffee with toast and Marmite. Then on to his much-documented Covent Garden office, which is a fascinating cornucopia of idiosyncrasy – Aladdin’s cave meets Willy Wonka’s factory. It is lined with bookcases stacked high with books, piles of fabric from exotic street markets, bits of origami, paintings and trinkets either collected on his extensive travels or sent in by fans.

Sir Paul’s success is founded on graft, honesty, humility, twinkly-eyed eternal optimism and good manners. He proves that you don’t have to be a self-serving megalomaniac to achieve in business. The rules that follow are as straightforward, unfussy and approachable as the man who devised them.