Check out the rad folks at the Urban Orchard Project, based out of the UK. They are an organization devoted to creating, restoring, and celebrating fruıt orchards in London and beyond. The video above provides a quick lesson on pruning old fruıit trees, and they provide more invaluable advice on their webpage.
Remnant Orchards, or what remains of traditional orchards, are valuable and often overlooked resources. They often have high genetic and bio diversity; can serve as food sources to urban populations; foster local character; and help make city spaces more pleasurable to inhabit. The Urban Orchard Project works wıth communities and activists to restore the health of these orchards by extending the life of old trees while newly-planted trees become established. This has the compound effect of providing continuous and long-lasting habitat for wildlife and producing food for human consumption.