The Spell of the Enchanter — Margery Hilton

Dave Merrow was determined to save the Marcombe Youth Centre. from the property developers, and Jo, because she adored Dave, was prepared to do anything to help him -- even to the extent of stowing away in the car of Sir Sheridan Leroy, the eminent Q.C., whose aid Dave hoped to enlist.

But how could Jo guess that the enigmatic Sir Sheridan would in his turn demand her help to further his own personal intrigue...?

Hero: Sir Sheridan Leroy
Heroine: Johanna "Jo" Medway