For years, a plaque at Balham Tube station paid tribute to 64 who died that night but a Wandsworth Guardian investigation found the number was higher.
It omitted the names of London Underground workers, believed to have been on shift or off-duty at the time of the blast.
Our investigation took us to the Imperial War Museum where a document suggested 68 people had died.
A Wandsworth Council register revealed the number the authority had accounted for was 67.
Our research forced London Underground to look at the plaque issue and last week - nearly three years after our initial inquiry - it put up a new plaque to mark the anniversary.
Confusion over whether 67 or 68 people lost their lives that night remains, but at least now the plaque commemorates all civilians and transport staff who lost their lives that tragic evening.
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