James Thompson: Tie-up hands Boots a 'new window on the world'

Walgreens says it filled 819m prescriptions in its last financial year

John Boot and Charles Walgreen would not have had the foggiest idea that more than a 100 years after they founded their respective companies, they would be heading towards a full-blown marriage.

But just 52 years after Mr Boot opened his first store in Nottingham in 1849, Mr Walgreen purchased a drugstore where he had worked as a pharmacist in Chicago.

While he manufactured his own line of drugs and opened its 100th store in 1926, it was his grandson, Cork, who drove its expansion from the 1970s. Since then, Walgreens has grown sales for 37 consecutive years to make it America's biggest pharmacy chain with sales of $72bn across nearly 8,000 drugstores.

Such a huge network means Walgreens sells countless health and beauty products in its stores and online, as well as offering pharmacy services.

Demonstrating its scale, Deerfield, Illinois-based Walgreens, whose chief executive is Gregory Wasson, a pharmacist, says it filled 819 million prescriptions in its last financial year.

In recent years, the US company has been acquisitive – albeit on a much smaller scale to today's mega-deal with Alliance Boots. For instance, Walgreens acquired Happy Harry's in 2006, adding 76 stores, primarily in Delaware.

In 2010, the US market leader purchased the Duane Reade drugstore chain in New York. Stefano Pessina, the chairman of Alliance Boots, yesterday described Duane Reade as a "window on the world" to showcase certain products.

However, unlike in Walgreens' stores in the US, Mr Pessina probably has no plans to sell cheeseburgers in Boots on this side of the Pond.