be required as a term of the loan to observe the solus tie. A growing trend in the late 20th century was for the brewery to run their pubs directly, employing a salaried manager (who perhaps could make extra money by commission, or by selling food). Most such breweries, such as the regional brewery Shepherd Neame in Kent, which claims brewing lineage back to 1698 and Young's in London, control hundreds of pubs in a particular region of the UK, whilst a few, such as Greene King, are spread nationally. The landlord of a tied pub may be an employee of the brewery—in which case he would be a manager of a managed house, or a self-employed tenant who has entered into a lease agreement with a brewery, a condition of which is the legal obligation (trade tie) only to purchase that brewery's beer. This tied agreement provides tenants with trade premises at a below market rent providing people with a low-cost entry into self-employment. The beer selection is mainly limited to beers brewed by that particular company. A Supply of Beer law, passed in 1989, was aimed at getting tied houses to offer at least one alternative beer, known as a guest beer, from another brewery. This law has now been repealed, but while in force it dramatically altered the industry. The period since the 1980s saw many breweries absorbed by, or becoming by take-overs, larger companies in the food, hotel or property sectors. The low returns of a pub-owning business led to many breweries selling their pub estates, especially those in cities, often to a new generation of small chains, many of which have now grown considerably and have a national presence. Other pub chains, such as All Bar One and Slug and Lettuce offer youth-orientated atmospheres, often in premises larger than traditional pubs. A free house is a pub that is free of the control of any one particular brewery. Free houses can, but do not necessarily, serve a varied selection range of guest beers. Some pub chains do so as well. Burton upon Trent For centuries, Burton upon Trent has been associated with the brewing industry due to the quality of the local water (from boreholes, not from the River Trent). This comes from the high proportion of dissolved salts in the water, predominantly caused by the gypsum in the surrounding hills; the resulting sulphate brings