Saw an ad for this in yesterday's londonpaper.
Basically, take your copy of thelondonpaper into any London branch, buy one Strawberry Cool Smoothie and they'll give you another for free.
They change the offer every week so that applies to different flavours
Please note: You have to take the whole paper in and offer is limited to one per person per day.
Cornhill (EC3), Curzon St (W1J), Canary Wharf (E14), Millbank (SW1), High St Ken (W8), Westway (W10), Jubilee Place (E14), BBC White City (W12), Ludgate (EC4), Rathbone Place (W1T), Strand (WC2), Eastcastle (W1W), Brunswick (WC1), Bankside (SE1), Broadwick (W1F), Notting Hill (W11), Strutton Ground (SW1), Bryanston St (W1H)