Lingua franca

I went to the house after work to catch up with the builders. My long list of short questions was quickly answered. As I was leaving I was puzzled by the language being spoken between the Polish-origin site manager (I have been in Poland, I often hear him speaking in Polish and I think I recognise the music of the language) and the Latvian-origin tiler (I haven't the first clue about Latvian but would have been surprised if the site manager spoke it).

Doh. Russian. I am relearning the Russian alphabet at the moment but I don't recognise the sound of Russian with a Polish or a Latvian accent.

They both also speak superb English but I think this conversation was a bit of humorous banter rather than hiding anything from me.