Lion Quality Eggs has introduced a way for people to tell when their eggs have boiled.

It is developing an invisible ink logo that appears on the shell in black when the egg is ready. Three types are available - soft, medium and hard.

Gilly Beaumont, from B&H Colour Change, which developed the logos, said: “We are still perfecting the technology, but we are very excited about the prospect of sorting a problem that has wound people up at breakfast time for decades.”