One explanation could be the crew of a previous landing or departing aircraft reported debris on the runway, meaning an inspection had to take place. have had this a couple of times at LGW in the past 2 years - we get onto the runway to take off and promptly turn straight back off again. The flight deck have then announced that the immediately prior landing aircraft reported debris. 5 minutes or so later we were off.

That damn video is so tedious, for a non-English speaker it must be appalling to try and follow.