Salisbury Hall, just off the M25 at London Colney near Hatfield and St Albans, is where the Mosquito was designed. In a fascinating museum on the site of rare de Havilland aircraft is the original Mosquito prototype. It still has some patched up hasty repairs that were done when it was on trial at Farnborough.
https://www.dehavillandmuseum.co.uk/?FORM=LFACTRE