In the UK, you must submit a substantial thesis (size dependent on field, typically 60,000 - 100,000 words (exc. refs and appendices)). The thesis must be defended during an oral examination (viva voce) to a panel of experts in the field (one internal to university, one or two external). The examining panel will not have been involved with your research in anyway. The thesis should provide evidence of novel research and show a contribution to knowledge in the field and it should be obvious from your performance at viva that you wrote the thesis! There is no requirement to publish work before a PhD is awarded but it's always good to publish ASAP.