The principle of the prohibition of double patenting is based on the idea that the applicant has no legitimate interest in proceedings that give rise to the grant of a second patent in respect of the same subject-matter for which he already holds a patent. There is therefore nothing objectionable in the established EPO practice that amendments to divisional applications are objected to and refused, when the same subject-matter is claimed in the amended divisional application as in a pending parent application or a granted parent patent. However, this principle could not be applied with a view to preventing the filing of identical applications, because that would infringe the prevailing principle that an assessment of the EPC requirements is made on the basis of the final version put forward (G 1/05 date: 2007-06-28, OJ 2008, 271 and G 1/06, OJ 2008, 307).

In T 2563/11 the appellants' line of argument that differences between the descriptions at issue might prove useful in finding fallback positions in any national revocation or infringement proceedings failed to persuade the board that they had a legitimate interest.