Installing Nest thermostat

[Russinating]

Installed a friend's Nest thermostat for them last night, I did mine for the second time a couple of weeks ago and so thought it'd be a simple job. It kinda was, power back on within 5 minutes but it's not calling the boiler for heat (power is fine and it's communicating with the thermostat).

I've tried the earth-coloured wire into both 1 and 2 on the Nest (common and call for heat respectively) but no luck. This was all their old thermostat:

I haven't tried linking the live to 1 on the Nest yet (as per old one) as couldn't quite tell from the wiring diagram if that was required and didn't want to blow the thing!

Any ideas? Is the above required?

 

[FlyingFish]

Copy what you have pictured above, but 1 is 2 and 2 is 3 on the Nest receiver (Heat Link).

 

[FlyingFish]

To explain in simple terms, Live (brown) to L, Neutral (blue) to N, Link req from L to 2, Black (re purposed Earth) to 3.