On 2017-12-12, ARW wrote:

http://www.bbc.co.uk/news/av/uk-engl...cycling-centre

Now is it me of did the bloke set it off? He did not just "pick it up
and it went off"

From watching the video, I guess he could have pulled "the pin out" or
something like that, but it certainly doesn't look like he lit it.
How do these kinds of flares work?