With all the fuss about Toyota and the sticking throttle issue on Lexus automatics, I wondered if it is possible to switch the FL2 auto gearbox into neutral in an emergency at 70 mph? Do you need to touch the brake pedal to change to neutral? Can it do any harm to the gearbox? Stornaway grey SE auto with 18" alloys

Yes, you can change to neutral, while moving, without pressing the brake.
And you can also switch back to Drive, while moving, without pressing brake, as long as your speed is above 10 km/h (6 mph) and you'll switch back to Drive in no more than 2 seconds.
It's a characteristic of all Aisin Warner auto gearboxes.

As a parallel, on VW cars equiped with Aisin Warner auto gearboxes - Touareg for example, that two seconds delay is even taken out. I.e., if you are in neutral and the car starts to roll away on a slope, as long as the car exceed 5 km/h, the lock is deactivated automatically and you can switch to Drive without pressing brake.
Usefull, because a brake press on a slippery slope could lock the wheels and roll over the car. In this way you just switch to Drive, without touching the brake, and use the engine brake (and Hill Descent if existing) option.

The gear lever is only a block of electrical switches which send information to gearbox ECU.
Gearbox ECU is the thing that takes any action based on your input, no matter how wrong it is.
If it can't be executed it will not be executed. So don't worry, it is "stupid proof".

Also, for the daring ones of you , you can switch to reverse while moving forward and you will see that nothing will happen as long as your speed ahead is greater than 11 km/h (6.8 mph). ECU will prevent it. It is named "Reverse Lock-Out".

But be aware to NOT accidentally put it in Park when you are moving because THEN you will ruin your gearbox, as the park is the only unprotected mecanically element engaged by the selector lever.
What's happening when you switch to park is explaind here:
http://www.freel2.com/forum/post51629.html#51629