Hi Lodewijk,
In your reply to Olushola you said:
"I hope you can perhaps also clarify whether 'in English' means that the original article has to be available in English, or that some translation should be available in English."
As Shola hasn't provided any clarification on this, note that the FAQ[1] for the award states:
Q: My article is in French, Portuguese, Swahili, or any other language that is not English. Can I submit a translated version?
A: This year’s awards are focused on articles published in English. We are
not accepting translated articles.
Best regards,