Can't edit text when using OmniGraffle on the iPad Mini iOS 8.3

I’m running OmniGraffle 1.9.3 on an Ipad Mini and I can’t appear to edit text. I’m hoping it’s something obvious I’ve missed.

I can ‘lasso’ text elements, move, cut, copy, paste etc. I just can’t seem to edit the actual content.

have I missed something obvious?