Japanese firm Fujitsu is at the heart of the Post Office's IT scandal. More than 700 Post Office branch managers were convicted when faulty accounting software made it look as though money had gone missing from their sites. That software, named Horizon, had been developed by Fujitsu.

As the public inquiry into the scandal continues, Fujitsu's legal representatives will make their opening statements on Friday. So how did a Japanese company, generally known to Brits as a maker of laptops, become embroiled in one of the most widespread miscarriages of justice in UK legal history?

It may be difficult to believe, but in Fujitsu's home market, hardly anyone has heard of the Horizon scandal.

"Horizon? What's Horizon?" was the reaction of a former company president in Tokyo when the BBC asked him about it.

This is a person who worked at the firm for nearly four decades.

The current president, Takahito Tokita, has turned down our multiple interview requests, even when I asked for a written comment he may wish to make to the victims whose lives were turned upside down.

The Horizon scandal saw some sub-postmasters attempt to plug huge shortfalls with their own money, after IT errors made it appear like thousands of pounds were missing. Some even remortgaged their homes.

Hundreds ended up with criminal convictions for false accounting and theft, and some went to prison. Many were financially ruined and have described being shunned by their communities. Some have since died.

The assertion in Japan has repeatedly been that this is a matter that its UK subsidiary is handling.

To understand Fujitsu's role, let's go back to its takeover of the British firm International Computers Limited (ICL) - which developed the Horizon software - in the 1990s.

The relationship between ICL and Fujitsu goes back decades, and the ways in which both operate are quite similar.