The consumer, sports and entertainment specialist joins on 7 November as a senior account director with a remit to develop content, entertainment and sports at the agency.
Sketchley spent two and a half years at TVC and orchestrated global syndication of Red Bull Stratos and the Lloyds Bank Torch Relay at the 2012 Olympics.
On Friday it was announced that Porta Communications increased its initial 30 per cent holding in Thirteen to a 51 per cent controlling stake, valuing the new agency at £1.75m.