The Court of Appeal has overturned the High Court's decision on this case, which involved the resignation of a teacher, following her suspension pending investigation over allegations of using unreasonable force against two children. The High Court had ruled that suspension was not a neutral act and had concluded in the words of Smedley J in an earlier case of Mezey v South West London and St George's Mental Health NHS Trust [2007] EWCA Civ 106 that:

"… Suspension changes the status quo from work to no work, and it inevitably casts a shadow over the employee's competence. Of course this does not mean that it cannot be done, but it is not a neutral act. …"

The Court of Appeal has found that any such finding is not particularly helpful - Singh LJ noted the following:

"I can see nothing in the terms of the ACAS Code of Practice which says that suspension is a "neutral act." It does not say that. What it does say is that it should not be considered a disciplinary action and this should be made clear to the employee."

He continued:

"That said, it seems to me that the question whether suspension is to be viewed as a neutral act is ultimately not a relevant question nor a particularly helpful one. The crucial question in a case of this type is whether there has been a breach of the implied term of trust and confidence. In the context of suspension that in turn requires consideration to be given to the question whether there was reasonable and proper cause for that suspension. This is a highly fact-specific question. It is not a question of law. Whether or not suspension is described as a "neutral act" is unlikely to assist in resolving what is the crucial question."

Singh LJ referred to the ruling of Lord Steyn in Malik v Bank of Credit and Commerce International SA (in compulsory liquidation) [1998] AC 20, where he said that an employer shall not "without reasonable and proper cause, conduct itself in a manner likely to destroy or seriously damage the relationship of confidence and trust between employer and employee". Breaches of such terms constitute repudiatory breaches of contract which employees are entitled to accept by resigning.

In short, the real test when determining whether to suspend an employee is whether there is reasonable and proper cause. It may or may not be a neutral act but the employer must have good reasons for moving to suspension of the employee. The way that suspension is carried out could lead to a breach of contract (whether or not it's a neutral act), if there has been conduct by the employer which:
(1) destroys or seriously damages the relationship of trust and confidence; and
(2) is without reasonable and proper cause.

NB: Readers in Northern Ireland should not that the Labour Relations Agency's equivalent Code goes further than the Acas Code in GB in relation to precautionary suspensions of employees:

"In certain cases, for example in cases involving alleged gross misconduct, where relationships have broken down or there are risks to an employer’s property or responsibilities to other parties, consideration should be given to a brief period of suspension with full pay whilst an unhindered investigation is conducted. Such a suspension should be imposed only after careful consideration of the necessity for this. Employers should also consider alternative actions which would be more acceptable to the employee yet serve the same purpose as a suspension. An alternative to suspension might be the agreeing of a temporary transfer to other duties or another work station without loss of pay. Any action taken, including suspension on full pay, should be reviewed frequently to ensure it is not unnecessarily protracted. It should be made clear that any action taken is neither considered as disciplinary action nor an indication of blame or guilt..."
https://www.bailii.org/ew/cases/EWCA/Civ/2019/322.html