Submarine Has Attention-getting Protuberance
Could this really be secretive? The Silent Service is not that sloppy, unless it wants to be. Paint a submarine bright blue so it attracts immediate, worldwide attention and thousands of stares must be expected. To duck hunters this is the equivalent of using a flourescent orange decoy (attracting only primates) .
Consider, too, that Torbay like some of the UK's other T-class attack subs (the RN's most advanced nuclear fleet submarines pending the Astute class) are equipped with pump-jet propulsion - a high-pitch, low-revolution propeller much quieter than conventional propeller designs Remember, The Hunt for Red October?
The question was first noted in a UK submarine discussion forum. Curious, but for reasons given above, easily dismissed. A little later, in a posting about the new color, one Spearfish commented: More interesting is the bulge on the port side of the fin that should have been covered.
So, I casually checked for obvious answers only to find most photo viewers completely missed the strange protuberance (red arrows above) on the port side of Torbay's sail, as Vigilis originally had. Still disbelieving, I found another confirming photo here. And yes, older photos suggest it is rather new (although HMS Trafalgar is alleged to have had it under tarp at a 2005 ceremony in Portsmouth).
Since sub launched cruise missiles can be fired from horizontal tubes (which Torbay has), and because its location conflicts with missile storage and loading, we can rule out that application (Torbay was recently refitted for Tomahawks).
The sail location is consistent with other possibilities, however. The most promising (in my opinion) would be satellite uplink-related (and Torbay has been recently outfitted for that improvement, as well).
But since speculation is such fun, the most entertaining possibility in my mind relates to: this.
I am so glad that the UK is one of our greatest allies and very open to more likely possibilites, if you can peg one. Do submarines really have to surface to fire a high-power, aimable laser? Not if a telescoping mast with an articulating head fits inside this interesting tube.