Suitable derailleur for 12 to 35 cassette.

[Doug.]

Hello,can any one help me with the above ?
I have changed my 12 to 29 cassette for the above (long hills and old age are getting the better of me )
The bike has a 50 x 34 compact crank and 10 speeds, all Shimano.
I realise that the existing mechanism has only a short :medium cage shifter and I need a long cage either road or mountain bike derailleur to enable gear shifts with such a big cog.
Advice , type or model of shifter I need will be would be a great help.
Thank you.

 

[Spiderweb]

This will do the job.
http://www.wiggle.co.uk/shimano-rd-m670-slx-10-speed-shadow-rear-derailleur/
Have you bought a longer chain too?

 

[Ajax Bay]

Advice , type or model of shifter I need

Think it would only be fair to say which STI you recommend for OP's drop bars, to go with that RD, @Spiderweb

 

[boydj]

My understanding is that if you use a Shimano MTB derailleur, you will need a 9-speed derailleur which will work with a road 10-speed shifter. The pull ratio of a 10-speed MTB derailleurs is different to that of road mechs.