Tracking race-running friends at the London Marathon was a logistical nightmare in the pre-smartphone days.
Back then, you'd need to plot pace estimates against a course map to find out when and where you should stand to offer your 'moral support' (which was, by pure coincidence, right near a great pub beer garden).
Luckily, there are now some techier ways to track your runner's progress in the race, which starts at Blackheath this Sunday 23 April. Here's our pick of the best...
If they're a Strava fan...Strava Beacon
Six months ago Strava switched on a new feature called Beacon, which lets Premium subscribers (from £5.99 p/month) share their real-time location with up to three people (who don't need to subscribe or have the app).
Beacon was mainly designed as a safety feature to help you keep tabs on someone who's out on a long run or ride, but it's also a potentially handy way to track the progress of your Strava-loving marathon runner - particularly if they're already planning to use the app on race day.
A word of warning: although the feature has worked brilliantly for us so far, we haven't yet used it in a marathon context. And the London route's tall buildings are known to cause issues with GPS and cellular signals for runners and supporters alike.
Like all tracking options, there are potential issues with battery life and cellular signals, but Strava Beacon's ability to send location updates every 15 seconds makes it a potentially more accurate alternative to the official London Marathon app (see below).
If they're a 'serious' runner...Garmin LiveTrack
If your marathon-running friend wants you to have all of their live stats, including heart-rate, cadence and elevation, along with their location, then Garmin's LiveTrack is your best bet.
It only works with a few Garmin watches - the Forerunner 230, 235, 630, 735XT and Fenix 5/5S/5X. But assuming they've got one of those (and as they're a serious runner, they probably do) they'll be able to start a Livetrack session in the Garmin Connect app on their phone.
Of course, this means having to run with their smartphone, a potential deal-breaker if they're trying to shave seconds off their PB. But if not, it's then just a case of sharing a web link with you via email, Facebook or Twitter. There's even an 'auto-start' option, in case they get distracted on the start line by the prospect of running for four hours straight.
If they want to run smartphone-free...Virgin Money London Marathon app (iOS)
If your runner doesn't fancy carrying a smartphone on their London 'adventure', then this official app is your best bet for updates on their progress. As long as you're using an iPhone.
Add your friend's name or bib number to the 'favourites' section and you'll get their estimated position every 5km, based on timings from official race chips given to each runner.
It's not quite the same as live-tracking someone for the whole race, but the app will also predict the time your runner will get to the next 5km checkpoint based on their current pace. You can follow the progress of celebrities too, which this year includes, er, Katie Hopkins and Scouting for Girls.
The Marathon promised that the official app would be available for Android too in 2017, but so far there's no sign of it in the Google Play store. We'll update this if it materialises in the nick of time.
Best of the rest...
If you're ruled out of using the three tracking solutions above, you do have a few more options.
The most clunky but battery-friendly will be to go the official website via your phone's browser, where you'll find a link to the tracking service used by the official app.
If your runner doesn't use Strava or Garmin Connect, there's a chance they might subscribe to Runtastic Pro or Runkeeper Go, which both also offer live-tracking options. Runkeeper has posted some handy instructions on how to use its tracking service.
Lastly, if you've lost your smartphone or need an emergency backup, head to page 12 of the official Spectator's Guide for a table of time estimates for different running paces. You'll be back to the dark ages of plotting time estimates on a race map, but at least it won't lose mobile signal or run out of juice.