An injunction was granted against ASLEF after the union included two members in a ballot who were not entitled to vote, 605 people altogether.
It also argued that the union did not provide accurate information in the notice of its intention to hold a strike ballot.
Although the common law recognises no right to strike, there are various international instruments that do: see for example Article 6 of the Council of Europe's Social Charter and ILO Conventions 98 and 151.
The law requires that the figures are "as accurate as reasonably practicable in the light of the information in the possession of the union at the time when it complies with [the obligation]".
The focus on the information actually in the hands of the union at the time when it complies with its obligation is, submits Mr Hendy, crucial.
He relies in particular on the following obiter observations of Lloyd LJ in Metrobus: "It is relevant in this context that the 2004 amendments included provisions, at section 226A(2D) and (2E), and correspondingly in section 234A, which limit the obligation imposed on a union in this respect, by a reasonable practicability criterion and by defining restrictively the information which is deemed for this purpose to be in the possession of the union.
First, in my judgment Mr Béar's argument simply fails to give any weight to the fact that the reasonably practicable duty is limited by reference to the information possessed by the union.
In my view, to require this would simply be to set traps or hurdles for the union which have no legitimate purpose or function.
In my view the courts should not take the draconian step of invalidating the ballot, thereby rendering the strike unlawful, simply because the term used to describe a particular process is infelicitous.