https://www.bbc.com/news/uk-23957605
Capt Campbell wrote a letter to the German emperor begging to be allowed to go and see his mother, which the Kaiser allowed - as long as Capt Campbell gave his word that he would return.
Capt Campbell wrote a letter to the German emperor begging to be allowed to go and see his mother, which the Kaiser allowed - as long as Capt Campbell gave his word that he would return.
Mr van Emden said that Capt Campbell almost certainly travelled through the Netherlands and then by boat and train to Gravesend in Kent, where he spent a week with his mother before returning to Germany the same way.
His mother died in February 1917.
Mr van Emden told the BBC that Capt Campbell would have felt a duty to honour his word and "he would have thought 'if I don't go back no other officer will ever be released on this basis'".