Not a dupe, Works, Once per account.
This offer entitles all GLAMOUR readers to 20% off ASOS Collection full-price items only at ASOS.com between August 11 and 23:59 on September 8, 2014.
Enter discount code ASOSGLAMOUR at the checkout.
Valid for one transaction only per customer, up to maximum of £500 (before discount is applied). Offer cannot be used in conjunction with any other promotion. Some exclusions may apply. Not valid on gift vouchers, optional delivery charges, ASOS Marketplace or ASOS Premier subscriptions.
http://www.glamourmagazine.co.uk/news/fashion/2014/08/11/aso…
seems to work on non-ASOS products as well.