Mayonnaise

I'd love to make my own mayo successfully. I've tried a few times by hand using olive oil. Perhaps too strong a flavour. Marcella says use vegetable oil and the blender. Neil Perry says not to believe her, and to use virgin and extra virgin olive oil and whip by hand.

I tried Marcella's.

It tasted ok (not great) but didn't come together from a thickness perspective. It was runny like thin gravy. I put in an extra egg yoke but to no avail. Any tips on this one? Obviously I've done something wrong.

Marcella says commercial mayos are "beneath discussion" and I believe her. But how to make the real stuff properly?