Mortgage prisoners are homeowners who typically took out a mortgage before 2008, when lending rules were more relaxed. They're now trapped on pricey mortgage deals unable to switch to cheaper ones, mainly because they don't pass newer strict affordability tests. With some paying interest rates as high as 9%, the picture is pretty bleak.

Northern Rock failed over 2007-2008 due to a number of factors, least not of which was the housing downturn and the Financial Crisis that rocked the UK at that time.

Northen Rock’s existing mortgage customers at the time needed servicing and the Government stepped in and took the bank under state control in February 2008. Part of Northern Rocks business was considered to be "good" whilst other elements were more difficult for the Government to off-load as they were consider by the market to be "bad".

The problem then became that consumers forming the so-called bad element of Northern Rock (including things

like interest only mortgages) found themselves with new companies owning their mortgage obligations who were not properly equipped to do so. In essence these new lenders did not offer (or did not originally offer) new mortgage products to their customers. New, tighter mortgage lending rules also meant that these same mortgage customers struggled to qualify for a new, cheaper mortgage elsewhere. As a result, these consumers were trapped into their existing mortgages paying excessively high rates of interest and unable to find a better product.

Importantly, despite previously qualifying for a mortgage, the stricter mortgage application rules implemented by many lenders because of the financial crisis created a bizzare situation where some home owners no longer qualified for new mortgages, even though in many cases they were already paying more on a monthly basis than the cost of newer mortgage which clearly demonstrated their ability to pay.