In fact, it did have a release catch, but not in the usual position just under the bonnet. It was under a grill, set into the bonnet, as I discovered when my hand just seemed to slip in there...! "Blarst, boy," Hughie told me, "you'd mearke a hoolly good mechanic, you would!"
Not wishing to get my hands mucky, I made my excuses and left (it was near elevenses time), but my Little Willie wasn't so keen, and took three kicks to be persuaded!