I'm sure everyone who has travelled on them extensively has already figured this out, but Virgin Trains have come clean and admitted that the design of their new Voyager and Pendolino trains cuts off mobile phone reception.
As a regular traveller on the cross-country route it's been very obvious to me that reception in the new trains is a lot poorer than it used to be, with many more patches where there is little or no signal.
However Virgin also said that they were in the process of testing signal boosters onboard carriages to improve the mobile reception, and that if these tests were sucessful the boosters would be rolled out over the entire fleet. But there really isn't such a thing as a signal booster for mobile phones, so I'm guessing that they may actually be experimenting with picocells.
Now this is interesting because it means they might also be experimenting with onboard wireless. GNER has been rolling out wireless on it's Mallard services running along the east coast mainline since July, and as far as I'm concerned, onboard wireless is the holy grail of train travel. I'd be quite willing to pay through the nose for it if Virgin introduced it on the routes I normally travel...