Lego copied a rival brick — it didn't grip. The tube system fixed it and built an empire

In 1947, the Lego Group — a Danish company that had been making wooden toys since 1932 — purchased a plastic injection-moulding machine. In 1949, they began producing 'Automatic Binding Bricks' — small plastic bricks designed to interlock. The idea was not original. Lego had received a sample of the 'Self-Locking Building Bricks' invented by English toymaker Hilary Fisher Page, whose company Kiddicraft had patented the design in 1939. Godtfred Kirk Christiansen, son of Lego's founder, later admitted under oath that they had copied the English bricks 'very carefully.'

The early Lego bricks had a critical flaw: they did not hold together well. The locking mechanism was weak, and a stack of bricks would fall apart with a slight bump. The bricks were not versatile enough for creative play. Lego had a product that could not do what it was supposed to do.

In 1954, Godtfred Kirk Christiansen saw the potential in the bricks as a system for creative play. The technical problems remained. On 28 January 1958, Godtfred filed a patent for a redesigned brick. The key innovation was a system of hollow tubes on the underside of the brick. The tubes improved the clutch power dramatically — the bricks now stayed together firmly but could still be pulled apart by a child. The 'clutch power' was the breakthrough that made the Lego brick work.

The modern Lego brick became the foundation of the most successful toy company in the world. The original inventor, Hilary Fisher Page, never saw this success. Kiddicraft went bankrupt, and Lego acquired the remaining patents and moulds. Godtfred's tube system — the fix for a flaw in a copied design — had created a system that would outlast every competitor. More than 400 billion Lego bricks have been produced since 1958.