I'm sure it will be fine Neil, but my concern would not be with the beam, or the padstones it's sat on, but the potential for deflection in the corners of the building. I would have either designed a 'goal post' frame or fixed steel angles into the internal corners to stiffen the building up.
I suppose most things have to be belt and braces designed these days. Years ago building were put up and altered with little thought to these things, and they're still standing.
Simon