Thank you for your question
My name is Clare
I shall do my best to help you but I need some further information first
Was any Case Law referred to?
My apologies for the delay
Were you represented or acting as a Litigant in Person?
I ask because this is a complicated issue and there is Case Law on both sides.
However the case that sets out the basic test is
Re Northall (deceased) 2010
The basis of this is
"1. When one person puts money into joint names there is a presumption of a resulting trust to the provider of those funds. The presumption can be ‘rebutted’ if the circumstances give rise to something called the presumption of advancement, which was not the case here (and which this article does not go into), or, by evidence that the provider intended to transfer the beneficial interest;2. The burden of proving such an intention is on the person who is alleging it."
The latest case is
Drakeford v Cotton and Stain  EWHC 1414(Ch)
But I am afraid that this is not likely to be of assistance
Please ask if you need further details
What was the relationship between the deceased and this person?
In fact it is the case of
Which has caused the problem
Has your Uncle been alive then the Northall Case would have protected you.
The fact that he has died means that
Drakeford v Cotton and Stain  EWHC 1414(Ch) applies
More specifically here
"The 3rd possibility received much greater analysis and was found to represent the true intention of the widow. The judge observed that this result was not easy to analyse or describe. However, in essence, his view was that a. The legal title was in joint names b. One of the account holders was entitled to draw on the account and the money drawn was their sole property c. The other account holder was not entitled to draw on the account d. On the death of one account holder the accounts belonged absolutely to the survivor, irrespective of who was the survivor. This structure removes the asset from the free estate of the widow and is a trust structure."
I am afraid that I think this is a potential problem
I appreciate that it would not have arisen - but after his death the burden of prove changed form being that of the defendant to that of the claimant - which is why you lost.
You are most welcome