https://www.techradar.com/news/smart-ways-to-track-your-friends-at-the-london-marathon-2018

If you're heading down to the London Marathon this year, chances are you'll be wanting to keep tabs on someone when they're pounding the streets.

Whether that's just to make sure that someone is still going and not given up in the sweltering heat (I won't lie - it's starting to frighten me a bit) or just want to know how many times you'll be able to see them, knowing their current whereabouts is crucial.