Ramblers - and I think DP is a rambler, isn't it? - don't need much pruning except for a tidy up and taking out weak or congested stems after flowering. There are rose experts here, so I am sure they can help further.

Prune in September - in theory, all the stems which have flowered should be cut out at ground level, and the new stems tied onto a support, but in practice, this often means removing too much wood if not many new stems are present. If that's the case, retain the best of the old stems, cutting back their lateral branches to about 3 inches, and tie in the new growths.