This meant consumers were likely to be confused or deceived, amounting to a breach of the Fair Trading Act.
However Justice Rachel Dunningham, who heard the High Court appeal, disagreed, finding the marks were not similar enough to create confusion between Cadbury and Whittaker's products.
While she acknowledged there were "undeniable similarities between the individual words" used in the relevant trade marks, she agreed with evidence presented by Whittaker's showing "Black Forest" was more likely to be associated with flavours of a black forest gateau cake.
A key idea the Berry Forest mark brought to mind was the phrase "fruits of the forest", which was a term for a mixture of berries, Justice Dunningham said in her decision.
She considered the similarities between the two marks were "insufficient" to risk confusion or deception among chocolate-buyers.
Justice Dunningham dismissed Cadbury's appeal.