Passengers had a lucky escape when a section of the glass canopy roof which covers the platforms at Hammersmith Broadway Tube station caved in.
Shards of glass dropped on to the eastbound District Line track but missed passengers waiting on the platform, last Wednesday at noon.
Customers were evacuated and Tubes on the line passed through the station while engineers removed debris which had gathered in the canopy. Glass was cleared from the tracks later that night.
The incident could have been worse had the ageing panels, which have not been replaced since the roof was built 15 years ago, not been coated with protective spray that stopped much of the debris falling to the platform.
Transport for London, which admits similar failures to the roof have happened before, believes the latest incident was caused by last week's rise in temperatures, explaining that the canopy's support bars had got hotter, causing the glass to crack.
TfL is now looking at replacing the glass and maintaining the rest of the canopy this summer, and in the meantime is pledging to conduct regular inspections of the structure when temperatures rise again.
An anonymous passenger who was waiting on the platform at the time of incident contacted the Chronicle to say: "It's really worrying that the problem hasn't been fixed when I've seen it happen before.
"TfL need to do something about it sooner rather than later before someone gets injured."
A TfL spokeswoman confirmed the incident, saying: "Staff kept passengers away from that part of the eastbound District line platform as a precaution as well as arranging for the shattered glass to be removed.
"Contractors arrived on site within about half an hour to remove the shattered glass from the roof. While the glass was being removed from the roof, Tube trains were not stopping at the station.
"Contractors removed some glass from the track at night when the trains had stopped running so that the District line service was not disrupted during the day.”