Quick thinking from engineers prevented cement from setting in the Victoria Line signal room which would have caused even further disruption to commuters.
Peter McNaught, operations director for the Bakerloo, Central and Victoria lines, said it was lucky workers knew sugar would stop the cement setting.
Normal service has resumed on the line after engineers worked throughout the night to repair the damage.
More top news
Prince Harry's Invictus Games is hailed a success as it closes with star performances from the Kaiser Chiefs, Ellie Goulding and Diversity.
Levi Roots from Brixton is the UK's richest reality star and Leone Lewis also makes the Top 10, but how did other Londoners fare?
The mayor is expected to be joined by his wife when he asks local Conservatives to choose him as their candidate in the general election.