It has to be declared if anything over 5% according to substantial shareholder notice regulations
Therefore.... either someone with a crap load of cash (albeit maybe borrowed here?!) is an absolute idiot and went over the threshold without thinking it through....
Or they believe they've got as many as they could, and saw an opportunity for another 0.5% or so at a good price, which took them over the 5% tipping point.
Or something more sinister that I'm hopeful against, and ignorant of...
Perhaps they've put all that they're able to on this horse, and ready to watch the race themselves?