Margaret Harrow is half of the comedy duo 'Harrow and Wealdstone', her partner being Bridget Wealdstone. In Hidden Underground, John Collier finds himself on the bill with them at the 'Square World' club in Euston. In Over the Top, they are due to appear at the 'Earl of Watford' pub in South Kensington, where Tony Tulse reveals that he saw them at Square World and thought they were brilliant.
In Off the Rails, it turns out that Margaret was Ava Sudbury's best friend at college, and that they had a comedy double-act together until she ran off with Ava's then boyfriend Gordon Hill. Harrow and Wealdstone have now become very successful and appear on American TV.