Having studied linguistics I'd say the claim is sensationalist rather than sensational. English is a rather wild crossbreed of many European languages, all of which share the same Indo-European roots.

Old English is very closely related to Old Frisian and Low German. Later on English has been heavily influenced by Scandinavian, Romance (mainly French due the Norman invasion in 1066 - Norman French to be specific, which differed quite a bit from Île-de-France French at that time) and Gaelic languages to some extent.

You'll find salient features of any of these language roots but that doesn't make English a Romance or Gaelic language for instance, it's just that it has been influenced by those and hence adopted grammatical features.

The main reason for this is that Great Britain before the times of the British Empire was one of the most contested places in Europe.

Finally, some of the claims in this article are somewhat inaccurate. There were no Scandinavians and British people at that time, 'Danes' and 'Anglo-Saxons' would have been the correct terms.

I also have a problem with the claim that Norwegians find it easy to learn English because their languages are so closely related. The same has been said about Dutch not long ago.