In this video, Llywelyn travels to Wales in 2018 on a Kingdom of Wales diplomatic passport to issue a challenge to the UK after the UK Cabinet Office acquiesced (1) on the fact that Llywelyn is the true King of Britons.

The UK was unable to charge Llywelyn with fraud or having a fake passport because it is an established fact (manifesta probatione non indigent) that he is the de jure sovereign of Wales. By placing himself at risk Llywelyn was able to extract a declaratory recognition of sovereignty (2) from the UK. Any other person would have been charged with a crime for traveling on a self issued passport. The UK did not want him to have a trial, as a trial would reveal a lack of jurisdiction and expose the fact that the UK is only an acting government and not the true sovereign government of Wales.

Under international law, a government in exile has the authority to perform all normal acts of state. Including the issuing of identifications, passports, and creating treaties and alliances with other governments. 

The paramount take away from this video is that the United Kingdom is not the sovereign government of Wales. Their presence in Wales is an occupation under international law (3).  The Kingdom of Wales exists in present day, entitled to all of the signs and symbols of sovereignty and independence. 

Cymru am byth!
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(1) "Delay by an individual claimant in the presentation of a claim has at times been held to bar the right of a state to present the claim subsequently as a valid one in international law. The grounds for the refusal to allow claims under these circumstances have been variously expressed. At times the disallowance is merely stated in terms of the claimant's non-action or laches, and at other times in terms of prescription or of a limitation on international claims.”
Marjorie M. Whiteman, Damages in International Law 236 (1937)

(2) “The declaratory doctrine of recognition can be stated in simple terms. A State exists as a subject of international law-as a subject of international rights and duties-as soon as it "exists" as a fact, that is, as soon as it fulfills the conditions of statehood as laid down in international law. Recognition merely declares the existence of that fact. These propositions are regarded by the adherents of the declaratory view as self-evident.”p. 423
H. LAUTERPACHT, “Recognition of States in the International Law”, “Yale Law Journal”, Volume 53, Issue 3, Article 1,  (1944)

(3) “Occupatio bellica, or belligerent occupation, is “quintessentially a temporary state of fact arising when an invader achieves military control of a territory and administers it on a provisional basis, but has no legal entitlement to exercise the rights of the absent sovereign.” Nehal Bhuta, The Antinomies of Transformative Occupation, 16 Eur. J. Int’l L. 721, 725 (2005)” 
See  Melissa Patterson, “Who’s Got the Title”, Harvard International Law Journal, Volume 47, Number 2, Summer 2006