Himalayan Blunder

A very very serious mistake is called A Himalayan blunder.

From Missouri

This means the person requires strong evidence before he believes anything.

Dunkirk Spirit

When people combine together to get over a difficult period, we use this idiom.

Cut The Gordian Knot

This means solving a very complex problem very simply.

Crossing The Rubicon

When we have no returning back, i.e. only one option is left with us we use this idiom.

Coals To Newcastle

Doing something which is totally unnecessary or worthless.