A major philosophical difference between the UK and USA halves of the SIGINT tribe, and between the tribe and the military, was who the intended customer for intelligence was. The Americans were traditionally very keen on bringing everything back to Fort Meade for processing and analysis, and then feeding intelligence reports to the top level of government. As very often, the British followed suite, but only up to a point. GCHQ as an institution was traditionally very concerned with its status as a direct contributor of intelligence to the core executive, co-equal with MI6, the diplomats, and the armed forces' Defence Intelligence Staff. In fact, as we saw in part one, in some ways it had greater independence and status - as well as its own private diplomacy with the Americans, it also has the unique privilege of sending the prime minister intelligence outside the formal processes of the Joint Intelligence Committee machinery.
In practice, though, it was often more interested than the Americans in pushing information forward to the military in the field or to diplomatic posts. This was influenced by the British specialisation in ELINT, which tended to be more interesting to the military and more dependent on collection from their ships or aircraft, and also by the Bletchley heritage. ULTRA's triumphs weren't just about Alan Turing or about computers; a huge problem that had to be solved to make it useful was the distribution of highly secret information to the army in the field in near real time. (A key motivation was that GCHQ was well aware that the Germans were in the habit of breaking Allied cyphers, and then transmitting the results over their ENIGMA and FISH radio networks - allied traffic turned up in the take all the time.)
It's probable that a major reason why GCHQ wasn't more like that, rather than less, was that the American approach was useful politically. Supplying the Cabinet directly obviously helps to win the budget wars. Similarly, too much emphasis on tactical work might give the impression that the agency was a support service to the armed forces, rather than something like a fourth service in its own right. Horrors.
But this didn't stop some important projects from being designed to fill the gap. GCHQ had been called in to investigate whether the Territorial SAS's stay-behind reconnaissance teams, intended to target the Red Army's rear areas for air (and specifically nuclear) attack, were likely to avoid getting caught for long enough to be useful. They demonstrated that, even using burst transmissions, the Soviet electronic-warfare units would very likely triangulate on them within 24 hours. This obviously wasn't good enough, and one of the results was the Nimrod R1, the RAF's airborne electronic intelligence system. System is the right word; as well as the planes, the project included a special RAF intelligence centre at Wyton, communications links forward to the army, and the capability to have intelligence analysts, Army liaison officers, or linguists actually fly on the plane with the radio operators. (As well as the R-1s, the Nimrod MR2s have done a lot of this in Afghanistan, and paid the price.)
That was then; the RAF is now leasing three RC135 aircraft from the Americans, actually older than the R1 airframes and designed for the model then considered inappropriate.
This may be a serious problem; one of the big questions facing GCHQ is the age of fibre-optics and open-source cryptography. With less and less telecoms traffic going by satellite or microwave, and less of that going in the clear, what to do? Further, the questions aren't the same ones as they were in the cold war.
An example of why this is relevant is this piece by Spencer Ackerman on the US Air Force's MC-12 aircraft and its role detecting improvised explosive devices in Afghanistan. In fact, as he points out elsewhere, the MC-12 (roughly, a Beech King Air stuffed with sensors, extra fuel, and spooks) does a lot of other things too, although they're mostly classified. It's an example of a current trend - rather than UAVs, there's increasing interest in cheap light aircraft carrying the latest sensor packages. This has the advantage that they can take up intelligence agents and work more closely with the troops, as well as being cheap.
There's much more detail here, which makes the interesting point that the role of Task Force ODIN, set up to kill insurgent bombmakers in Iraq, is now a broader one in support of the counter-insurgency strategy. This changes their relevance from being purely tactical and military to being political and strategic. They haven't been inactive on this - from Aldrich's site, here's a fascinating data sheet on their backpack SIGINT kit, the ideal gift for the geek who has everything and a death wish and very similar to some Rohde & Schwarz mobile network testing gear.
Speaking of mobile networks, Aldrich also confirms that a capability to listen to cellular networks exists, mounted on the British Army's three Islander aircraft - it's not clear from his discussion whether this means the access side or microwave-backhaul, or whether this relies on the old A5/0 and A5/1 cyphers still being in use.