[rjsw]

The tower block wasn't originally built with the cladding that burnt.

The idea was that the tower is almost all concrete, a fire on any one floor shouldn't spread as there is little to burn. The problem is that later modifications to the heating system and the addition of the cladding have changed the design a lot.

[_delirium]

Fwiw regulations actually have been getting more conservative on this. There was more confidence in the 1970s (when this tower was built) that modern concrete construction didn't require sprinklers. With the core construction material itself not flammable, and serving as fireproof separation between units, fires were supposed to be contained by design, with spread unit-to-unit throughout the building (especially so rapidly that it'd happen before fire services could arrive) not being possible due to passive suppression, and therefore not in need of active suppression. Which as you say may even have been true with the original design prior to interior ducting and exterior cladding changes.

In any case, in the past 10 years the consensus has been changing towards it being prudent to just always require sprinklers in high-rise towers. Scotland began requiring them in 2005, and England in 2007, but neither law is retroactive.