Started the car today and it was making an odd knocking/ticking noise and ive started it, restarted it, left it to run and driven it but there is no difference the noise is still there. Ive never had this noise before its always had a bit of pistonslap but its odd and makes me nervous. Any ideas what it is?

Video:
http://www.youtube.com/embed/dlaOrPuwPGo

Jamie