Synapse external table not accessible

Ive been playing around with Synapse today and I spent ages trying to troubleshoot an external table not working and trying all kinds of elaborate permission troubleshooting for something which was a stupid simple error.

The error I got was:

Started executing query at Line 35BatchId: 0, record affected: -1(Encountered empty schema.)External table 'dbo.HelloWorldPopulations' is not accessible because location does not exist or it is used by another process.
Total execution time: 00:00:00.448

It turns out the url for the location is case sensitive.

Id used:

blogmsdemofs/raw/helloworld/SloveniaTestData.csv

I should have used:

blogmsdemofs/Raw/helloworld/SloveniaTestData.csv

CREATE EXTERNAL DATA SOURCE [HelloWorld]
WITH ( 
    LOCATION = 'https://[my_dl].dfs.core.windows.net',
    CREDENTIAL = [WorkspaceIdentity]
)

CREATE EXTERNAL TABLE [dbo].[HelloWorldPopulations]
( C1 nvarchar, C2 nvarchar, C3 nvarchar, C4 nvarchar )
WITH
(
    LOCATION = 'blogmsdemofs/raw/helloworld/SloveniaTestData.csv',
    DATA_SOURCE = [HelloWorld],
    FILE_FORMAT = [PopulationFile]
) ;

Hopefully this saves someone else wasting a few hours trying to work this out