I'm sure many readers are familiar with Bernard Cornwell's 'Sharpe' novels, and the TV series made from them.
For the TV series, musician John Tams played the role of Daniel Hagman, one of Sharpe's 'Chosen Men'. He also adapted an old English folk tune into a Peninsular War-era soldier song, which was used as the theme song for the entire series. I'm well schooled in English folk music, and I thought he did an excellent job. Here he is singing it.
(For details of the images used in the video, see its page on YouTube.)