NSEU, keep imagining.
tubby linton et al, “…would you expect all your pitot systems to be affected…”
The problems which I am familiar with involved the TAT probe (fully heated), and has been observed in association with engine malfunctions due to unusual icing conditions (refs below).
In unusual circumstances, the atmospheric temperature and water/ice content of the air flowing through the TAT probe can match the heat flow of the heater. Thus, ice can form in the probe resulting in a ‘high reading’ of zero degrees (same as the ice).
IIRC there have been rare events involving some pitot probes, which if blocked will lock in the pressure conditions present at that time. Presumably, in the same conditions all systems could be affected simultaneously.
N Europe in May? – Yes, see the maps for the problem locations!
AIRA - Collaborations - Propulsion System Icing
SAE Aircraft & Engine Icing International Conference: 2007 Session Presentations
http://www.skybrary.aero/bookshelf/books/581.pdf
http://www.flightsafety.org/asw/jun0...n08_p12-16.pdf
AERO - Engine Power Loss in Ice Crystal Conditions
Airline Regulators Grapple With Engine-Shutdown Peril - WSJ.com