I know this question sounds silly, but here goes.
I will be in London this July of 2017, and will need to use the tube. I was in London back in 2010 and got an Oyster card which I was not able to return. I still have it. If I brought that Oyster card with me to London this year, would I still be able to load pounds onto it and use for travel? Or is it too old for that?