I thought so too. The racial lines are not the same as before, both being Dravidian. The Madurai Nayak Dynasty, being Dravidians ruling over much of modern Tamil Nadu, I think could be called Tamil. They did make Tamil a court language in Kandy at the time.

The last four Kings of Kandy were all Nayakars spanning over a time period a little less than a century.
Sri Vijaya Rajasinha 1739-1747
Kirti Sri Rajasinha 1747-1782
Sri Rajadhi Raja Singha 1782-1798
Sri Vikrama Rajasinha 1798-1815

Kirti Sri Rajasinha did much to advance Buddhism in Sri Lanka, which at that time had fallen into decline. On the initiative of Ven. Weliwita Saranankara (1698–1778) the Thai monk Upali Thera visited Kandy during the reign of king Kirti Sri Rajasinghe (1747–1782) and once again reestablished the Buddhist order in Sri Lanka in 1753. (Wiki Siyam Nikaya)

Kirti Sri Rajasinha also built the Raja Maha Vihara (Gangarama) at Kandy and the existing inner temple of the Sacred Tooth Relic. Kirti Sri Rajasinha also got the the Mahavamsa chronicle to be continued from the time of Parâkkamabâhu IV down to his own reign.

Another King of Sri Lanka who was completely foreign was Nissanka Malla (1187–1196), from Sinhapura, Kalinga (modern day Orissa). Think the time of the Norman Conquest of England. The buildings he erected were Nissanka Latha Mandapaya, Hatadage, Rankot Vihara the fourth largest stupa in Sri Lanka and a major refurbishment of the Dambulla Cave Temple.

There may or may not be direct bloodlines, but its unlikely that “HRH Regimus” is one of them.
See this comment at CeylonTamils.com that does actually trace family trees.

I know that you are honest and genuine, and I think Mr Kanagarajah definitely believes he is someone special, but I don’t think he has any right to call himself part of the Jaffna Royal family. There are lots of people who have a right to call themselves direct decendants, but I’m afraid I don’t think Mr Kanagarajah is a genuine direct heir at all.

I too have had a lot of contact with him. I was trying to help him find more information to substantiate his claim, but every single attempt failed. His claim to be connected to the Gardiners and the Ponnambalams is definitely not true – both families have never heard of him. I’ve asked them here in Colombo and they denied having any connection at all. I tried asking the Portuguese authorities if they had any information to recognise his claim – after all, the Portuguese have given him an award. It turns out that they believed him based on a search of the internet. When I asked him for more information, he grew angry at me and has not spoken to me since.

Here are my reasons for why I think he is a fraud:

1) He is not able to trace a father-son line to the Arya Chakravarti kings.

2) He claims to descend from Sankili Kumaran, and says that his ancestor ‘hid’ from the Portuguese and avoided being taken to Goa in exile. There is no documentary evidence of any such ancestor at all. Had there been a missing son, the Portuguese would have searched far and wide for him to bring the kingdom to an end. I can’t believe that they would have been completely unware that a son existed.

3) He claims to have proof of kingship because his family lived at ‘Sankili Thopu’. The Sri Lankan Government took over this property and have had it in their control for a number of years, but I’ve spoken to people who have grown up nearby and they’ve never heard of him or his family. If they were genuine, then those nearby would have known them.

4) Finally, when Mr Kanagarajah first approached me, he was several generations short of a credible family tree. It was only after discussion with me that he found three of four more generations of names.

5) There was a wikipedia article about him that was planted by another known pretender – claiming connection to the Vietnamese royal family. That guy was the subject of a wikipedia investigation and he has since been banned from editing wikipedia for pretending to be someone else. A news article about Mr Kanagarajah’s wedding was deliberately planted by him, suggesting that he was travelling in cognito. The whole article was plated. I checked.

All this adds up to a fraud.