help needed wiring in a smart thermostat

[e39darren]

can anyone help me please , i recently bought a Nest learning thermostat and im a bit stumped when it comes to wiring it in

i sort of know my way around basic electrics but its confused me when i found it is wired with 4 core plus earth wire .
I have got a worcester greenstar 28i boiler and it is connected through a serviceplus s17 timer ( i dont need that so i plan to take it out and simplify the wiring ) and has a wired thermostat in a different room , here is a picture of the wiring diagram for the boiler -



here is a wiring diagram for the nest thermostat and heat link ( ill be using the thermostat wirelessly so wont be using my exsisting thermostat wiring )





id be extremely grateful if someone could point out which wires i need to connect , thanks in advance

[e39darren]

thanks for replying and i think i understand now , does this diagram look right ? thanks

[e39darren]

hairyben said:

almost- 3 to lr

this the return line- which calls for heat

is this it

[e39darren]

hairyben said:

yup!

excellent , thank you very much top man

[e39darren]

moles said:

Awesome send that off to worcester as their new wiring diagram designer

im st hot with MS paint