A naval war during the Abyssinian Crisis

What happens if war breaks out between Britain and Italy during the Abyssinian Crisis?

The Italian navy is likely defeated, forcing withdrawals from East and North Africa and possibly toppling Mussolini.

Italy would be isolated during the Abyssinian Crisis because Germany was not ready to offer effective support. The Royal Navy would probably defeat the Regia Marina. Loss of sea control could force Italy out of Abyssinia and North Africa by cutting the position off from secure reinforcement. The political consequences might include Mussolini's fall and a very different Italian military program before 1939.