This will enable you to enter a tracking number for Royal Mail deliveries.

1- It will add a link in the customers order history, so if they click on the link it takes them to the tracking status of their order.

2- Once you have added the tracking number in the Admin side it will send them an email with a link to the Royal Mail website tracking page.

See Images for more info (I have a theme on my store thats why the images may look different to your version, but it will still work)