Answer ... The validity of UK patents granted by either the UK IP Office (UK IPO) or the European Patent Office (EPO) can be challenged before the Patents Court, the IP Enterprise Court (IPEC) or the comptroller at the UK IPO.

European patents are also subject to a post-grant opposition procedure at the EPO. This opposition procedure is essentially a post-grant revocation action at the EPO which, if successful, will revoke the European patent in all jurisdictions for which it was granted.

Answer ... For UK patents granted by the UK IPO or the EPO, the validity of an issued patent can be challenged by filing revocation proceedings with the Patents Court, the IPEC or the comptroller at the UK IPO. Any person may commence such revocation proceedings.

Proceedings before the Patents Court or the IPEC are commenced by filing a claim form, particulars of claim and grounds of invalidity. In the Patents Court, the grounds of invalidity must specify the grounds on which the validity of the patent is challenged and must include particulars that clearly define the issues relied upon (although these are at a relatively high level). In the IPEC, it is also necessary to set out concisely all the facts and arguments relied upon. Revocation proceedings before the comptroller at the UK IPO are commenced by filing Patents Form 2 and must be accompanied by a statement of grounds that includes a concise statement of the facts and grounds on which the claimant relies.

For European patents granted by the EPO, the opposition must be filed at the EPO Opposition Division within nine months of publication of the mention of the grant of the European patent in the European Patent Bulletin. To commence an opposition, it is necessary to file a notice of opposition, which includes the grounds of opposition.

Answer ... The main grounds on which a patent can be invalidated in the UK courts are as follows:

• The invention is not a patentable invention (ie, lack of novelty (anticipation), lack of inventive step (obviousness), lack of industrial applicability and/or relating to excluded subject matter);
• The patent was granted to someone not entitled to it (although this ground can be raised only by someone claiming to be entitled to the patent);
• The specification of the patent is not sufficiently clear and complete to enable the invention to be performed (ie, insufficiency);
• The matter disclosed in the specification of the granted patent extends beyond that disclosed in the application as filed (ie, added matter); or
• The protection conferred by the patent has been extended by an amendment which should not have been allowed.

In addition, invalidity challenges before the English courts increasingly include an allegation that the teaching of the patent is not plausible. Although not specified as a particular ground for revocation, plausibility issues arise in relation to arguments that a patent lacks an inventive step, lacks industrial applicability or is insufficient.

Answer ... The evidentiary standard to invalidate an issued patent in the United Kingdom is the ordinary standard in civil litigation generally: namely, the overall ‘balance of probabilities’.

Answer ... It is not possible for third parties to oppose the grant of a UK patent at the UK IPO. It is possible for third parties to file written observations to the comptroller during the prosecution phase, but the third party has no right to be heard or to be informed of any responses from the examiner or the applicant to such written submissions.

There is a post-grant opposition procedure for UK patents granted by the EPO. Any person can file an opposition at the Opposition Division of the EPO within nine months of the grant of a European patent.

Answer ... For applications for European patents filed with the EPO, any person may file written observations with the EPO in relation to the patentability of the invention during the prosecution phase. As with the UK IPO, persons filing such observations have no right to be informed of responses from the examiner or the applicant. However, unlike patents granted by the UK IPO, on the grant of a European patent, any natural or legal person may file an opposition to the grant of the patent. Opposition proceedings in the EPO can take several years to be resolved.

Answer ... European patents may be challenged in opposition proceedings in the EPO within nine months of publication of the mention of the grant of the European patent in the European Patent Bulletin.

Answer ... Oppositions at the EPO can be based only on the following grounds:

• The subject matter of the European patent is not patentable within the terms of Articles 52 to 57 of the European Patent Convention;
• The European patent does not disclose the invention in a manner that is sufficiently clear and complete for a person skilled in the art to carry it out; or
• The subject matter of the European patent extends beyond the content of the application as filed (or, in the case of a divisional patent, the parent application).

Answer ... There are three possible outcomes to opposition proceedings:

• The opposition is rejected and the patent is maintained as granted;
• The patent is maintained in an amended form (in which case a new patent specification is published); or
• The patent is revoked.

Answer ... The EPO will resolve the opposition proceedings on the balance of probabilities, based on the grounds or evidence relied upon by the opponent. The burden of proof is on the opponent to prove that the patent is invalid.

Answer ... Decisions of the EPO Opposition Division can be appealed as of right to the EPO Technical Boards of Appeal. The grounds of appeal are the same as the grounds of opposition.