Apple and Samsung will return to the Court of Appeal in London today in the latest round of their global patent wars.
The two tech titans are currently embroiled in a series of lawsuits around the world as they continue to do battle over copyright, with billions of dollars at stake.
The latest case focuses on their tablet computers and Apple's claim that Samsung's Galaxy tablet copied its design for the iPad.
Apple lost the first round at the High Court in July, when the judge ruled that the Galaxy was not as "cool" as the iPad and that it gave a different overall impression, so did not infringe its copyright.
Apple will now find out if it has been successful in its appeal against the ruling.
Simon Clark, head of intellectual property at international law firm Berwin Leighton Paisner, told Sky News: "Given the huge popularity of the iPad, it was not surprising that Apple chose to appeal the decision.
"However, the judgment was given by a highly experienced and well-respected specialist intellectual property judge, and Apple will have an uphill battle to persuade the Court of Appeal to overturn his ruling.
"The Court of Appeal is always reluctant to interfere with a judge's decision on similarity comparisons, which are inevitably subjective, even if they consider that another judge may have had a different opinion."
The legal test for whether a product infringes another's registered design is whether it produces the same "overall impression on the informed user".
Judge Colin Birss ruled in July that whilst the view from the front was "very, very similar", there were significant differences in both the thinness of the tablets and the detailing on the back.
Judge Birss concluded: "The informed user's overall impression of each of the Samsung Galaxy Tablets is the following.
"From the front they belong to the family which includes the Apple design; but the Samsung products are very thin, almost insubstantial members of that family with unusual details on the back.
"They do not have the same understated and extreme simplicity which is possessed by the Apple design. They are not as cool. The overall impression produced is different."
Therefore, he decided, Samsung's tablets had not infringed Apple's design.
The judge ordered Apple to post the court's decision on its UK website for six months and to take out adverts in various national newspapers and magazines stating that Samsung's Galaxy Tablet computers had not infringed its copyright.
If Apple ultimately loses this case, it will have to suffer the indignity of publishing the ads and publicly stating that Samsung did not copy its design.
If Samsung loses, it could end up with a permanent ban on sales of its Galaxy tablet in the UK.
However, both sides still have one further option of an appeal to the Supreme Court and with the stakes so high it is likely that whoever loses will appeal.