On June 25th a British Tornado jet fighter fired a Brimstone missile at a fast moving small armed boat (of the type Iran favors) and hit the target. The Brimstone used its own radar to keep track of the target. This "fire and forget" capability makes jets, operating outside the range of any weapons on these small boats, capable of quickly and safely destroying many of these fast attack boats. This is not surprising as Brimstone was the most outstanding air-to-ground weapon used during the Libya campaign last year, and for much of the same reasons.
The British 55 kg (109 pound) Brimstone was originally developed as an upgraded version of the American Hellfire. Brimstone ended up as a Hellfire in general shape only. Weighing the same as the Hellfire (48.5 kg/107 pounds), Brimstone was designed to be fired by fast movers (fighter-bombers), not just (as with Hellfire) from helicopters and UAVs. Aircraft can carry more of these lightweight missiles. These are perfect for small targets, including vehicles that need to be hit without causing injuries to nearby civilians or friendly troops. This is what made Brimstone so popular in Libya.
A major factor in the success of Brimstone is its superior guidance system. Four years ago Britain added a dual-mode (radar and laser) seeker to Brimstone. Originally, Brimstone was to be just an American Hellfire with a British seeker (a miniature, millimeter wave radar) and configured to be launched from jets. Brimstone did that but never got a chance to show how effective it was until Afghanistan and Libya. The performance of Brimstone was particularly impressive in Libya because the missile was used so frequently. That got the Americans and French interested in using it as a highly effective anti-vehicle weapon for their fast-movers (jet fighter-bombers).
Hellfire was first developed three decades ago as a helicopter launched anti-tank weapon but has proved to be very useful against enemy infantry hiding out in buildings or caves. Hellfire later proved to be an ideal weapon for use by larger UAVs. The current version has a range of eight kilometers, while Brimstone has a range of 12 kilometers.
The Brimstone radar seeker makes it possible to use the missile in "fire and forget" mode. The laser seeker is more accurate (to within a meter or two of the aim point). When used on jet fighters there is a special launcher, hanging from a wing that holds three Brimstone missiles (instead of one larger missile).
The nine kilogram (20 pound) Brimstone warhead is sufficient to destroy vehicles, without causing a lot of casualties to nearby civilians. British fighter pilots have become quite good at coming in low and taking out individual vehicles with Brimstone missiles. Carrying a dozen Brimstones, a fighter-bomber can easily use all of them in one sortie, all the while staying out of range of ground fire.