Why is there rivalry between royal engineers and royal artillery?

If my memory serves me correctly, the Artillery were the first regular Army Unit raised towards the end of the 100 years war as the most Honourable Companie of Artillerie and it still exists as a Territorial Army Unit - The HAC.

I believe the (Royal) Engineers were the second regular Army Unit raised, Royal in brackets because they were not given a Royal charter for a few hundred years.

There is also the rumour that the Royal Artillery lost its blue lanyard to the Royal Engineers as a result of an Artillery unit running from it's guns in the face of the enemy, apparently a Royal Engineer unit rescued the guns, thus resulting in the Artillery being told to wear a yellow lanyard to signify cowardice. The rumour appears to be unfounded, but it is always a good reason for the 2 Corps to have a punch up.