Treaty on the Functioning of the EU

My constituents are particularly concerned about the 90% of prisoners repatriated from the UK under the European arrest warrant who are foreign nationals. Will the Secretary of State make a categorical assurance that under the arrangements she proposes there will be no delay in repatriating those foreign nationals from our prisons? We understand there have been considerable delays recently, and that numbers of those going have not been as good as they should have been.