Drum role please...
Okay, my precise, scientific measurements say, the turning radius for the Morgan 3 Wheeler is
about 44 feet (13.4 meters for those on the other side of the pond). I would ensure you have at least 45 feet in your turning circle to ensure you don't hit something.
I tested this in a large parking lot, using the 9ft wide parking spaces as a grid to use as my guide. My 2021 M3W has a standard setup and AVON tires. I tried starting with my tires straightforward, or if I started with the wheels turned, both left and right hand turns. My turn radius varied from about 42.5 feet, to about 45 feet. I just measured a couple of the turns and used the parking space grid to estimate the rest. So not entirely scientific, but should get you what you need to set up your turn circle.
With about a 45' turning radius, I learned on day one of ownership to never attempt a u-turn! You need a good portion of Texas to pull a u-turn, never attempt in the State of Vermont!

Enjoy!
Craig