Radio4 news has just covered this allegation.
It's not even an allegation!
As things stand, it's nothing more than a "something that needs to be investigated". Once they've investigated, then they might make an allegation. Or not, as the case may be.
Which raises the question of how David Walsh found out, because if procedure is being followed, the UCI shouldn't go public until after they have weighed up JT-L's response to their initial letter.
There is an aluminium-rich argument that this has been stage-managed by Team Sky and David Walsh, in order to show that Walsh isn't Sky's sockpuppet, and/or to cheaply offload a rider who hasn't performed this year, but that is implying Team Sky possessing PR madskillz that they have signally failed to show thus far (ref. Dr. Leinders).
The other theory is that there was a deliberate leak from within the UCI, possibly as a mistimed final shot from team McQuaid against Brian Cookson and British Cycling.
That the UCI have asked JT-L to explain apparent anomalies in his bio-passport is neither here nor there, he can't have been the only rider subject to this process, but the fact that this has got into the public domain before it should have done gives the affair a certain
arôme de poisson.
