 The location of her birth remains uncertain , but reputedly she was born either in her parents ' Westminster home at Belgrave Mansions , Grosvenor Gardens , or in a horse @-@ drawn ambulance on the way to a hospital . Other possible locations include Forbes House in Ham , London , the home of her maternal grandmother , Louisa Scott . Her birth was registered at Hitchin , Hertfordshire , near the Strathmores ' English country house , St Paul 's Walden Bury , which was also given as her birthplace in the census the following year . She was christened there on 23 September 1900 , in the local parish church , All Saints , and her godparents included her paternal aunt Lady Maud Bowes @-@ Lyon and cousin Venetia James . 
