Tldr; a tower block suffered a partial collapse as a result of a gas explosion in 1968. Changes to Building Regulations were made to mitigate against 'Disproportionate Collapse'

(Effect on legislation) 'Existing buildings were allowed to resist an explosive force of 17 kPa (2.5 psi), provided that the gas supply was removed and flats were refitted for electric cooking and heating.'

Such buildings with gas supplies today will have been constructed to comply with the amended regulations.