I am extremely keen on a particular PhD being offered by one of the weaker (RAE 3a) departments of a very good university. I've visited the department, like the supervisors, like the labs and above all am massively enthusiastic about the topic. However, the low RAE score is nagging me. What are your thoughts?

I don't think that the low RAE score should matter, after all 3a isn't that low. There might be reason for the score, such as the research is relatively new.

More important than the RAE score is where the funding is coming from. Research council funding suggests a good research culture at the department. Avoid university sponsored studentships they often have unadvertised conditions attached or are not index linked.

We would disagree with Stuart. 3a is not a good RAE score, however he is right to say it's not the be all and end all. Look at the publication history of your supervisor - is he publishing in the major journals in his field? (try ISI web of knowledge, if you have access to it).

If the project is research council funded this will be a good sign. However if the department itself is low on funds (which it may well be with a 3a score) then some of the resources you need for your research may be unavailable, out of date or shared between a large number of people. Check that this is not the case before you accept the position.

If the project is one that really inspires you then you should probably go for it. If not then you would be well advised to check out other options first.