Directions:

Cavendish's 2nd home 1782-1785, 34 Church Row - N51 33.33 W0 10.74.
Lockyer's home, where he had an observatory and observed helium spectral line, 24 Fairfax Road - N51 32.59 W0 10.73.
"1" = St. John at Hampstead Church, Church Row - N51 33.32 W0 10.85.