It Is Possible to Walk from London to Brighton

On my jogging course at 6 am this morning, there were quite many people walking along grazing land in Falmer. I asked a tall and fit old guy, 'Is it charity or something?'. He kindly explained to me that they left 10:30 am yesterday in London, and have been walking without stopping for charity. They were very close to the goal then.
I even didn't know that it is possible to walk from London to Brighton. What an impressive group of people.