At Euston fire station drivers in lorries, cars and taxis sounded their horns in support of the firefighters. The union's own fire engine was driven onto the station forecourt, with Johnny Cash's Ring of Fire song blaring from a loudspeaker:
We have been receiving a lot of public support today at picket lines across London.
There is solid support for the strike - but it is a sad day in some respects because firefighters don't want to be on strike.
More top news
People have been warned to stay safe in the record-breaking bank holiday heat ahead of the second day of celebration in Notting Hill.
The famous sound of the steelpan played a big part shaping the carnival as we know it today.
A 21-year-old man from Loughton was arrested at the scene on suspicion of causing death by dangerous driving.