Here's a likely sequence of events: paint begins to bubble-wrinkle around the "fold" in the tube, then a hairline crack that expands to total failure. Steel tends to give lots of warning, but your frame is cooked. Even robust steel tubing is one mm (less than 1/25th of an inch) and the ends and 0.7 mm in the middle. That's thin, my friend. The integrity of the structure is inseparably bound to its spherical cross-section.

Sorry, but be glad it's an LHT and not a Waterford or Rivendell that you'll be replacing!

All the best,
Mark