The High Court in London will hand down a judgment of more than passing interest today. Mr Justice Foskett’s interpretation of a Labour Party rule will decide whether Jeremy Corbyn remains leader of Her Majesty’s Loyal Opposition in Westminster. Democracy hangs on the decision. The political elite – and the mainstream media – would like nothing better than to see the back of a man who threatens a comfortable consensus.

The rule in question says: “Where there is no vacancy, nominations may be sought by potential challengers each year prior to the annual session of party conference. In this case any nomination must be supported by 20% of the combined Commons members of the Parliamentary Labour Party and members of the European Parliamentary Labour Party. Nominations not attaining this threshold shall be null and void.”

This is unambiguous. In the current situation it means a challenger will require the support of 51 MPs and MEPs. But it is argued that Mr Corbyn – the target of a coup – must also get the same number on board as the rule does not explicitly say he is exempt from meeting this threshold. In short what is not excluded may be included.

I have been at the receiving end of this ‘argument’ while trying to defend a National Union of Journalists’ agreement about how performance issues should be resolved. Here is the relevant section of the agreement.

Agreed Statement E1a2 Issues of Capability

1 Introduction

The appraisal process is concerned with improving the performance of all staff. However, there may be occasions at the time of the appraisal when a manager identifies a level of performance which is unsatisfactory. There may be occasions when at other times a manager identifies a rapid and significant reduction in the level of performance. In these circumstances, it is important that specific action, outside the appraisal, is taken to help the member of staff improve performance.

2 Informal discussion

A primary objective is to ensure that staff who show signs of poor performance are given the opportunity and encouragement to improve. In these circumstances managers will discuss aspects of performance with a member of staff on an informal basis. Only when the manager determines that an individual has not responded to informal feedback and performance has fallen to an unsatisfactory level will the steps outlined below be implemented.

3 A programme to achieve improvement

Where a manager concludes that a member of staff’s performance is unsatisfactory, the manager may require the individual to complete a programme to achieve improvement subject to following the steps outlined below:

a) If a manager identifies that a member of staff’s performance is unsatisfactory and appraisal discussions and/or informal discussions have failed to result in improvement, the manager will meet with the member of staff to identify the reasons for the unsatisfactory performance and explain clearly the improvements that are required. Subject to the discussion, the outcome of the meeting could be a programme to achieve improvement; this would nominally be for a period up to six months.’

Referring to the agreement in her judgment EJ Hilary Harding said: ‘This set out that there may be occasions where performance issues have to be addressed outside the appraisal process. The policy suggested that informal discussions about the employee’s performance should be held first of all. The process did not specifically say that improvement plans could be used as part of the informal process, but neither did it prohibit it. It stated that only when the manager determined that an individual had not responded to informal feedback and performance had fallen to an unsatisfactory level would certain further steps be taken. These further steps were that a manager may require an individual to complete a ‘program to achieve improvement’

Paragraph 2 clearly says that only when the informal process has failed can the further steps, described at paragraph 3, be taken. These may include the implementation of a plan to achieve improvement.  In any case including what is not explicitly excluded in paragraph 2 is not enough.  Paragraph 3 also says such a plan may only be implemented after the informal process has failed. To satisfy Judge Harding’s conclusion that a formal plan can be imposed at an informal stage it is also necessary to exclude what is expressly included in this paragraph.

The tribunal’s finding had serious implications. It rendered the agreement meaningless and sanctioned the re-interviewing of senior journalists for their posts at the whim of management. More plainly it allows the BBC to continue to weed-out dissidents.

It is unlikely that Justice Foskett will accept a similarly flawed argument advanced by lawyers for millionaire Labour Party donor, Michael Foster. But the winds of change are blowing and there is more litigation to follow.