The great British breakfast started out really in the inter-war years before really taking off in the 1950s and 1960s, helped being popularised by the growth of tourism and it being served at B&Bs. Whilst eggs and bacon will have been eaten for breakfast from about the 18th century this would have been in wealthy homes only. The pre-cursor of the great British breakfast would have been the multi-course pre-hunt feasts that wouldn't have contained baked beans but would have also included things like quails and lobsters.
Baked beans can be traced back to the Victorian age when Fortnum and Mason started stocking them. As their availability and affordability increased so did the popularity of what is now recognised as the traditional English fry-up and they became a staple part of the great British breakfast.
