London Fire Brigade said it received 124 x 999 calls during the strike period, and contingency crews attended 17 incidents in the capital, including the large fire at a Dagenham scrap metal yard.
A recall notice was issued to crews due to the scale and seriousness of the Dagenham fire, which was ongoing as the strike started.
The FBU immediately advised firefighters that they did not agree that the protocol could be invoked and to ignore it.
Emergency cover was provided from 13 strategic locations by 27 fire engines and around 200 Emergency Fire Contingency Crew staff.
More top news
A time-lapse video has revealed how Ai Weiwei’s artwork Forever was taken apart.
The mother of Alice Gross has told an inquest the family have unanswered questions about the circumstances of her death.
Official figures show speed cameras are targeting thousands of drivers in London as they drive to work in the early morning.