I have a family member who has been in this situation and best thing to do is just spend the money on a service offered by someone you trust and is unknown to your wife and collect it later. You want to spend it in a traceable way so your wife and her lawyer knows its spent. The last thing you want to do is simply take the money out and hide the money if your wife already knows about it. You need to show that the money has been spent in a non-recoverable way to avoid her lawyer requested you to present your banks records etc.
Also if you setup a trust it will be defeated if your wife challenges it as
@Sols says as it was not established in good faith and there have been cases of challenges to such a trust successfully won by spouses. Most trust lawyer in channel islands will in fact will not setup a trust for you in this situation if they know its to avoid a pending legal case as they ask you this in the
due diligence as I found out for a family member. And I would not advise lying either as the trustees will dissolve the trust if they get any hint of foul play in its establishment.