Disregarding an admission of obviousness made by the patentee's expert witness during cross-examination in Nampak Cartons Ltd v Rapid Action Packaging Ltd [2009] BL O/342/09, a Patent Office hearing officer has refused an application to revoke a patent relating to sandwich packaging on the ground of obviousness because to do so would require him to work backwards from the invention.


Rapid Action Packaging Ltd was the proprietor of a patent for a sandwich carton in which the lid could be bonded to an outturned flange by heat sealing. During prosecution, the patent was narrowed to cover only such a carton that had been adapted by way of what is known in the trade as "concora cuts" in the flange. Under this method, when the carton is opened, the flange delaminates, leaving part of the flange material bonded to the lid.

Nampak Cartons Ltd sought revocation of the patent on the grounds of obviousness. Each party had experts who were cross-examined. Nampak's counsel led Mr Clough, Rapid Action’s expert, through a series of questions that led to his agreement on the concora cuts in the flanges sounding “like a sensible approach”. However, Mr Clough noted that, at the priority date, there would have been considerable prejudice against "interfering" with the flanges and that he himself would have avoided them.


The parties were in agreement that the notional skilled person was likely to be a team comprising a packaging designer and a packaging systems engineer.

The state of the art at the priority date was also agreed: triangular prism-shaped sandwich cartons made from cardboard were commonplace and the use of heat-sealing was wellknown, as was the "concora" method of providing tear strips, although it was not widely used in sandwich packaging at the time. Instead, the experts agreed that it was more usual to use a single score line at the reflex angle of the fold lines.


The hearing officer, Mr Probert, concluded that the inventive concept in Claim 1 was a cardboard sandwich carton with dual parallel lines of partial cut along the flanges, one being at the junction between the flange and the wall adjacent the inside of the flange so that the flanges could be split (i.e., delaminate between the cuts) to allow the lid to be opened.

Mr Probert found himself unable to accept that putting the concora cuts in the flange was one of two alternatives that the skilled person would consider and that it would, indeed, be a sensible approach. He concluded that some of the things that Mr Clough agreed with in cross examination were, in the words of Moulton LJ in British Westinghouse v Braulik [1910] RPC 209, "arrived at by starting from something known, and taking a series of apparently easy steps."

Accepting Rapid Action's submissions on "mosaicing", Mr Probert noted that, whilst it was tempting to put together a combination of prior art documents to show how the inventor may have arrived at the inventive concept, this would require a significant degree of hindsight.

It was clear from Pozzoli/Windsurfing that the assessment of the prior art must be made "without any knowledge of the alleged invention as claimed" and that since there were no cross-references between the prior art documents, they must be taken separately.

Mr Probert found that the difference between each of the prior art documents and the inventive concept constituted one or more steps that would not have been obvious to the person skilled in the art at the priority date. Accordingly, the application to revoke the patent should not succeed.


The case provides useful revision on the Windsurfing test and yet another reminder that mosaicing, however tempting, is not allowed.