with an almighty clattering soundtrack

I turned it off immediately and really don't know what to do next. I'm very nervous of making things worse! Here's the shortened video complete with horror soundtrack.
https://youtu.be/0aFR833yeLk" onclick="window.open(this.href);return false;
I could try starting the bike again and see if the noise settles down but that potentially ends with a £250 cheque coming my way from you've been framed for a video of my bike going bang and then me sobbing next to a broken bike. However I'm not sure what to check next without stripping the engine down and even then no idea what I'm looking for and that could still end with the same video

If it had started straight away after the accident I would probably have just let it run to see if it quietened down but the fact it didn't want to turn over or start for so long after makes me very nervous that the engine was locked somehow and something's damaged in there.
Opinions and suggestions sought...