Ann: Change in substantial holding, page-12

In the latest announcment I see this:

Nature of relevant interest(s):

Beneficial Owner For that relevant interest,— (a) number held in class: 1,190
(b) percentage held in class: 0.0003%
(c) current registered holder(s): Not applicable
(d) registered holder(s) once transfers are registered: UBS AG London Branch Nature of relevant interest(s): Prime Broker that has exercised its borrowing right in respect of shares pursuant to a Prime Broking Agreement For that relevant interest,—
(a) number held in class: 22,959,475 (b) percentage held in class: 5.26%

(c) current registered holder(s): Not applicable
(d) registered holder(s) once transfers are registered: UBS AG London Branch

Not sure what, if anything, I can make of that.

London branch buying up large for their investment portfolio? Or ultimately buying on behalf of some 'Beneficial Owner'?

Others may have experience in this area, any thoughts or feedback are welcome.