Ok I just tested that out. I uploaded a 1.5 minute video to We Transfer. You put in the email address you want it to send to plus your own email address. It uploaded and sent, and what was received was an email with the heading xxxxxxxxxxxxxxxxx@email address sent you "Video title name" via WeTransfer. Then in the body of the email it repeats that, along with a message (which you can add when uploading the video). Eg it could say "PLease find attached exhibit d for case no xxxxxxxxxxxxxxxxxxxxx". Then there is a download link so they can download the file.
It would need to be sent separately to the main statement and evidence in that case and you could say in a covering email that exhibit d is a video that would be sent by separate email from WeTransfer.
On the other hand - if you can upload the video direct to an email it's the same thing really. Except it could take a long time for the email to arrive or it might crash and not arrive at all. So if you did upload the video to a court email - I would do that as a separate email to make sure the rest of the statement and evidence gets there. WeTransfer is probably the safer bet to make sure the file arrives.