Ron,
There is no record in the online National Archives index relating to a Board of Enquiry for the event. However, in my experience, that is only Round One.

For example, there are many Boards of Enquiry reports within documents indexed under ‘Actions with the Enemy’ or ‘Actions against the Enemy’. If your uncle was lost in an action involving Axis forces there is a much better chance of finding something.

Also, there is a manual card-index system that cross-references many subjects inside documents, whereas the online index is limited to the title and description of the document.

HMS Express was a destroyer, so there is a good chance she was not alone on that (or any other) date: therefore there may be a war diary for the Command in which she operated that will cover the event.

If you can visit the National Archives in person, or have someone do it for you who is armed with all that you know on the event, there is a reasonable chance of finding documents that shed light on what happened.

There are other places to look if The National Archives has nothing.

Hope this helps, let me know if you get stuck.

Bruce