In UK law, the wishes of a person who has left a will are paramount.

This means that a will is valid so long as it's been filled out correctly and can be shown to reflect the person's true wishes.

This applies even if the will doesn't distribute their money, possessions and property (or 'estate') in a way that was expected or desired. A will doesn't have to meet the family's expectations to be legally valid.

However, if you think a person's wishes aren't reflected in the will, it's possible to mount a legal challenge to contest the will. You can also mount a challenge if you believe it hasn't been written according to the correct procedure.

This is a complicated process – and a costly one. Because of this, you need to decide if the end result is likely to be better than the will in its current form.

If a will is deemed to be invalid, it's usually replaced by an earlier version – but if there is no earlier version, the person has died "intestate" (without a will), and their estate is distributed according to the rules of intestacy. Before embarking on a legal challenge, it's important to decide whether this outcome is preferable to the will being executed as it stands.

A quick note on language. The legislation covering wills dates from 1837, and a lot of the language used sounds like it's come straight out of a Dickens novel – "testator", "codicil", "executor" and so on. In this article, we'll use layman's language where possible, or define terms when they crop up.

Let's take a look at what makes a will valid and the grounds on which you can contest it. We'll also briefly touch on the recommended timescale for doing so.

What makes a will "valid"?

A will has to meet a number of criteria to be considered legally valid by the probate court (the institution that deals with wills). It has to be:

1. In writing.
2. Signed by the deceased, or signed at their direction and in their presence.
3. Intended by the deceased to be valid.
4. Signed in the presence of two witnesses.

If these four criteria are met then the will has been properly "executed" and is legally valid – unless there are grounds to contest it.

What are the grounds for contesting a will?

As we said up top, the wishes of the will writer are paramount. As long as these wishes are reflected in the will, there are no grounds for a challenge.

A will can be contested if you have a belief or suspicion that:

1. The person who died didn't have the required mental capacity

Mental capacity refers to a person's ability to make a decision for themselves.

This is a complex issue as a person might have a condition that means they're considered able to make one decision for themselves but not another. In the context of wills, a person has mental capacity if they can understand, retain and apply the information relevant to writing the will.

If you think these criteria don't apply to the deceased, then you can contest.

The key questions surrounding mental capacity are:

• Did the deceased understand what they were doing when they wrote the will?
• Were they fully aware of what their estate consists of?

Under the Mental Capacity Act, it's presumed that a person has capacity unless it can be proved otherwise. If a claim of mental incapacity is made, the court will consult medical records and a medical expert to determine whether any impairment led to a lack of capacity at the time of writing.

2. The deceased lacked "knowledge and approval"

This is when there's a concern that the person who died didn't fully understand and approve the contents of the will.

This could be the case if the deceased was hard of hearing, had a speech impediment or was visually impaired – all of which could act as a barrier to full knowledge and approval. Similarly, knowledge and approval could be lacking if they had a low level of literacy, or were frail and unwell.

3. The deceased was under duress

Let's say there's been a last-minute or unexpected change to the will – one that seems surprising, out of character or detrimental to their estate. In this situation, there may be a suspicion that the person was unduly influenced or coerced into writing their will in a certain way.

If you challenge a will on these grounds, the onus is on you to provide proof that the writer of the will acted against their real wishes – and you have to prove that there's no other reasonable explanation for the will's contents.

This is difficult to prove as manipulation, coercion and undue influence typically take place behind closed doors by a partner, child or carer.

4) The document is forged or fraudulent

As you'd expect, a forged will isn't legally valid.

To prove that a will has been forged, a handwriting expert has to decide whether the testator's signature is genuine.

Relatedly, a will can be challenged on grounds of fraud – if, for instance, someone is impersonating the deceased for their own gain.

Reasonable financial provision

A final reason for challenging a will is if you depended financially on the person who died, but they made no provision for you. This typically applies to spouses and civil partners, cohabitants and children, but it's a challenge that can be brought by anyone who can demonstrate that they depended financially on the deceased.

When should a will be challenged?

Contesting a will is a complex process. Each case is unique and has to be made with reference to the character of the deceased, their family's dynamics and any wishes or intentions they shared with family members, friends and third parties. The recollections of these people are crucial – but as time goes by, memories fade, and it becomes increasingly difficult to mount a case.

Because of this, cases should be brought up as soon as possible – and while it's technically possible to do so after the estate has been distributed, it's logistically knotty and will lead to further legal costs.

At Milners, we pride ourselves on being flexible, approachable, and person-centred. If you need help contesting a will, consider contacting us for a free legal consultation.