How to delete item in Bin "... cannot be modified or deleted because it is required by MacOS"? I'm on a 2014 MacBook Air, 10.14.5

A couple of weeks ago I did a quick sweep of my files and drives to get rid of junk, mostly old photos and videos I had accumulated that I didn't need/want anymore. Everything deleted fine, except for one .mp4 file. This file, it seems, managed to get into my Bin, but is now stuck. I would really like to get rid of it - it was copied off an old USB drive and is about 5GB, which is a lot when you only have 10GB free space.

When I drag it anywhere, it just copies. When the bin is emptied, I get the message "....mp4 can’t be modified or deleted because it’s required by macOS". 

I've looked for possible solutions, including turning off System Integrity Protection and reinstalling the OS but to no avail.
Please help! Sorry if I've missed any details
The '“…” can’t be modified or deleted because it’s required by macOS.' message is typically caused by ACL permissions set on the file which cannot be changed unless SIP is disabled. Obviously a 5GB .mp4 file is not system file that needs protection and has somehow may have had erroneous ACL permissions set on it.

One sure way of deleting this file without having to disable SIP or modify ACL permissions is to boot to  Recovery Mode, (⌘R when restarting the Mac), and then in Terminal (on the Utilities menu)... use the following command, e.g.:

rm -f /Volumes/Macintosh\ HD/Users/Your_Short_Name/.Trash/filename.mp4



The example command above assumes the main Startup volume is Macintosh HD, change as needed.
The Your_Short_Name is that which you normally see in Finder as the name on your Home folder.
If filename.mp4 has spaces in it, then escape with backslashes as shown in the example command.


Then type reboot and press enter to restart the Mac back to normal mode boot.




ACL - Access Control Lists See also the chmod manual page.
SIP - System Integrity Protection