When You’re Sent Documents by Mistake: Why the Court Says “Send Them Back”

As dispute resolution solicitors, we are often asked a deceptively simple question:

“If the other side sends me documents by mistake, can I use them?”

A recent High Court decision provides a very clear and rather sobering answer.

The case is Forsters LLP v Uddin [2025] EWHC 3255 (KB) and it arose out of a neighbour dispute in south-west London that escalated into satellite litigation, data protection claims and ultimately an urgent injunction hearing in the High Court.

Whilst the facts are unusual, the principles are not. This judgment is an important reminder that just because information lands in your inbox does not mean you are entitled to keep or use it.

What actually happened?

At the heart of the case was a Data Subject Access Request (DSAR).

Mr Uddin, who was in a dispute with his neighbours, made a DSAR to his neighbours’ solicitors, Forsters LLP. A DSAR is a statutory right under data protection law allowing individuals to ask organisations for copies of their personal data.

So far, so routine.

But something went badly wrong. Instead of receiving a carefully filtered DSAR response, Mr Uddin was accidentally given access to around 3,300 documents, including:

In short, this was not just a mistake; it was a serious data breach.

Crucially, Mr Uddin recognised this immediately. In his first email back, he expressly said the disclosure involved “privileged and confidential communications belonging to other clients” and described it as an indefensible data breach.

That initial reaction turned out to be very important.

So where did it go wrong?

After acknowledging the mistake, Forsters asked Mr Uddin to delete the documents.

He refused.

Instead, he argued that:

He then went further and began deploying privileged material in witness statements, including barrister’s advice on prospects of success and internal legal strategy.

At that point, Forsters applied to the High Court for an urgent injunction requiring the documents to be returned or destroyed and preventing any further use of them.

The key legal question: can you rely on a “mistake”?

The judge had to decide whether this was an “obvious mistake”; a well-established concept in English law.

In simple terms, if:

This applies with even greater force where legal professional privilege (i.e. a right to withhold documents from a third party and the court where it relates to advice provided by a solicitor or barrister to their client) is involved.

The judge had little difficulty answering that question here. This was, in his words, not just an obvious mistake but a ‘glaring’ one. The recipient, a legally unqualified individual, himself had identified it as such within hours.

But what if the documents prove my case?

This is where the judgment is particularly instructive for non-lawyers.

Mr Uddin argued, quite understandably from the perspective of a non-legally qualified individual, that the documents helped him show the truth and that it would be unfair to stop him relying on them.

The court rejected that argument completely. Why? Because legal privilege is absolute. The law has already decided that the public interest in people being able to speak freely with their lawyers outweighs the interest in revealing relevant evidence.

Put simply, you don’t get to use privileged material just because it helps your case, and you certainly don’t get to benefit from someone else’s obvious mistake.

This is one of those areas where the law draws a very firm line.

What about the data protection angle?

Interestingly, the judge agreed with much of Mr Uddin’s initial analysis: the disclosure was indeed a breach of data protection law and professional duties.

But that did not give him a licence to keep the data.

In fact, the existence of large volumes of third-party personal data (completely unrelated to the dispute) made the position worse, not better. The court was particularly concerned about the ongoing exposure of innocent individuals whose data had no business being in Mr Uddin’s hands.

Delay – did it matter?

Forsters waited several weeks before issuing the injunction application, having tried repeatedly to obtain undertakings for his to delete the documents disclosed from Mr Uddin instead.

The judge was critical of that delay and noted it might affect who was responsible for costs, but it did not defeat the application. Where privilege is at stake, the court’s willingness to intervene remains strong.

The outcome

The High Court granted the injunction in full. Mr Uddin was ordered to:

The court’s aim was to put matters back, so far as possible, as if the mistake had never happened, whilst recognising that Mr Uddin cannot ‘unknow’ the content of documents he had already read.

Why this case matters

This judgment is a timely reminder of three important points:

In disputes, emotions can run high and temptation can be strong. But this case shows that courts take a very dim view of parties trying to capitalise on obvious errors, particularly where confidentiality and privilege are concerned.

When in doubt, the safest course is also the simplest one: stop, don’t read further and get advice.