How have courts dealt with a loan that turns out to be illegal?

In the case of Eha v. Genge, infra, para. 43, a loan was made between friends and business associates which turned out to be at an illegal rate of interest. It was found that the "parties ... did not have an illegal purpose or an evil intention" and "[n]either of these individuals particularly viewed what they were doing as illegal."( para 11 and 12) The court held that "to allow the respondent to evade responsibility for repayment of the principal amount of these loans would be to give him an undeserved windfall." (para. 12) The borrower was ordered to repay the principal amount of the loan plus court ordered interest, to be calculated under British Columbia's equivalent of Alberta's Judgment Interest Act.