Today, it transpires, is the anniversary of the Anglo-Portuguese Alliance, the oldest political / military treaty in existence, signed in 1373. The treaty set out terms for a perpetual alliance between England and Portugal which has pretty much lasted intact to this day.
That said, there have been moments. Portugal was subsumed by Spain a few times, and Spain has been an historic rival to England over the years. In those moments, whilst sometimes technically at war, England was usually working with the deposed Portuguese leaders to get them reinstated.
A more dramatic moment occurred in 1890 with The Portuguese Ultimatum (not a Bourne film). European nations were vying to take control over as many African territories as possible and the English / British felt that the Portuguese had wandered into land that was rightfully theirs. This led to a strongly worded memo threatening violent retaliation unless the Portuguese withdrew. This they did, but the feeling of national humiliation and disappointment in their monarchy helped fan the flames of the Portuguese republican movement, leading to revolution in 1910.
Stamp of the Day 