Oxford's announcement is here. Some friends on FB were puzzled that the endowment wasn't used to create a new Chair. I suspect the explanation is that the White's Professorship was not endowed at all, but supported by regular university funds, and that this endowment will take some of the strain off of Oxford's budget, which is very strained post-Brexit. 2.8 million euros in endowment will produce spendable income of about 80-100,000 euros per year, which would likely cover half or more of salary for the position. Comments are open for readers who may know more.
ADDENDUM: As pointed out in the comments, the endowment is in GBP, not euros, so the income from the endowment is likely to support more like half to two-thirds of the salary.