[drSteve78]

Those aren’t ‘UK solders’ - those are mercenaries

Hessians could be paid to fight for either side.

[TheDandyMan]

They aren’t mercenaries, they’re duly-sworn members of the regular Ukrainian military who are British nationals (assuming they are indeed Ukrainian Marines, there’s certainly been articles in past years highlighting the program that allowed foreigners to join regular Ukrainian units). The terms of service usually include receiving Ukrainian citizenship after certain requirements are met, to my understanding.

Incidentally, Hessians were auxiliaries, not mercenaries. Mercenaries fight of their own accord, whereas the Hessians and troops from other german principalities were hired out by their governments without input from the troops. In some instances, the rulers of the petty states received more money for a soldier killed than a soldier who returned alive.