How long does the Transport of a Gas Molecule take from Norway to the Alps?

Gas Market

During the last EXXETA training on fundamentals of the gas business a participant asked how fast gas travels through pipelines. As the training deals with commercial contracts and processes the question was deemed quite relevant. Imagine the following situation: A German station employee notices a sinking pressure on the manometer, hurries to the telephone and askes the Norwegian colleague to turn on the tap of the gas supply system. How long will it take until this event will show its effects in Germany?