Good morning #icfp2017.pic.twitter.com/jfndNHr523
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
TXL
LHR is def a thing on BA. 
Though I'd recommend waiting until Thursday so you can attend the Oleg workshop. 
One way? Are you planning on being dead?
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.