Lester Basil Sinclair

{{Use dmy dates|date=July 2019}}

{{Infobox person

| name = Lester Basil Sinclair

| image = Lester Basil Sinclair.jpg

| alt = Black and white photo of a man focusing on writing sheet music.

| caption =

| birth_date = {{Birth date|1894|08|29}}

| birth_place =

| death_date = {{Death date and age|1974|10|05|1894|08|29}}

| death_place =

| nationality =

| other_names = John Mystery

| occupation = Author, songwriter

| known_for =

}}

Lester Basil Sinclair (29 August 1894 – 5 October 1974) was one of the most prolific Australian songwriters during World War II. At the same time, Sinclair was an important Australian children's book author under the pen name John Mystery,Marcie Muir, A Bibliography of Australian Childrean's Books (London: Deutsch, 1970), p.443 publishing over 300 books.[http://www.slv.vic.gov.au/latrobejournal/issue/latrobe-60/t1-g-t4.html John Mystery: The Nation's Storyteller] La Trobe Journal, No 60 Spring 1997 Sinclair was born in Yorkshire and emigrated to Australia as a teenager.

He built a turreted 'John Mystery's Adventure Castle'{{Cite web |title=John Mystery's Adventure Castle |url=https://localhistory.sutherlandshire.nsw.gov.au/nodes/view/211347 |access-date=2023-09-10 |website=Local History - Sutherland Shire Libraries |language=en}} on the tip of the Illawong Peninsula in Sydney where he wrote many of his children's books. The mock castle no longer stands, but one of its ramparts serves as a castellated retaining wall on Cranbrook Place and several bas-relief sculptures remain in gardens on the same street.