There are several secure trailer tools.
But when watched YouTube I did observe that many pad locker can be easly open or damage. The same about chains.
And what is the reason to secure trailer hitch if someone can unscrew hitch and use his own ...
Finally I think that any secure is better than nothing.
I did invest in PEWAG chain (Austria company made chains for big machines and cars)
Maybe I trust too much below mentioned advert:
In US this chain cost 100 USD + VAT + shipping
In Poland (PEWAG Poland) less than 50 USD.
I hope that you have PEWAG UK and can buy it cheaper also.
VIRO INOX from Itally via eBay 50 EUR
Stainless Steel Armoured Padlock 'PANZER' | Viro Padlocks
Locksmith Glenwood Springs to Aspen, Safes Vaults & Commercial
I will try to:
Fix trailer to some solid item like lantern.
If it be not any maybe secure hitch by chain to not allow unscrew it or use hook.
Someone warned me in Croatia to secure trailer next time when I return to pick it up from not secure parking area for trailers.
He told me that sometimes some lost happens ...