" A knight in shining armour "
A person who comes to the aid of another when other hopes have faded, like the knights in romantic stories.
She was stuck, out of petrol in the middle of the moors at night. When the repair man turned up she called him her knight in shining armour.
Where did it originate?:
The United Kingdom. An allusion to the notion of gallant and noble mediaeval knights.
Where is it used?:
Widespread but not commonly used.
Hear the idiom spoken: