Wikipedia posted:

Madness then announced plans for a reunion concert, Madstock!, which was held at Finsbury Park, London on August 8 and 9 of that year.[29] The original lineup reunited, performing together for the first time since Mike Barson left the band in 1984. Over 75,000 fans attended the weekend festival, and during "One Step Beyond", the crowd danced so much they caused an earth tremor which measured over 4.5 on the Richter scale.