What part did ‘word of mouth’ play in the success of Boots’s ‘miracle cream’?

Alliance Boots is one of only three retailers (including Tesco and Marks and Spencer) in the UK to break the £1 billion profit mark, with profits in the 2012–13 financial year reaching £1.27 billion. All three retailers notably have steady, strong marketing strategies. Boots is by far the largest specialist retailer of beauty and toiletries in the UK, with sales of £22 billion per year. It has strong brand elements: the logo with its rich blue colour is easily recognisable.
The British anti-ageing skincare industry is estimated to be worth over £6 billion and Boots is the largest player in this market. One of its biggest success stories has been the No7 Protect & Perfect serum, which competes very strongly with well-known branded anti-wrinkle products.
It was clinically tested for 12 months before its launch in 2004 and claimed to contain renewing, protecting agents which scientists said repair photo-aged skin and improve fine wrinkles; 30ml of the serum is sold in attractive, cleanly designed packaging at a price [at the time of writing] of £16.75, a mere trifle compared with some other brand offerings priced in excess of £300.