Robins at War?

On the allotment plot today we were initially surprised that there were no robins around. It didn't take long for "Robbie" to appear once we'd started digging though!
However, he had a friend with him. I say friend. This may not be the case. They appeared to be having a Sing Off! Such a lovely duet - hopefully you can view and hear it on the video uploaded here...

After singing their little heads off for a long time, they sat in the hedgerow in some sort of Mexican standoff for a few minutes and then OUR Robbie (on the left) seemed to win the day and the other one disappeared off somewhere.

So, I think probably, it wasn't a mating ritual but a territorial issue. Robins are renowned for being extremely territorial.