The voucher which can be found on the O2 Priority Moments app entitles you to a 5 pack of men's Christmas socks worth £10, for just £1 at any BHS retail stores only. Offer is not available online.
Item Code - 61F61FBLK
Would make a good Christmas present.
Seems to be the same code O2SOCKS14 for everyone - somebody should post a screenshot.