Britain is being gripped by its biggest ever 'firewave' as wildfires blaze in 19 locations during the third heatwave of the year and heat health warnings were extended.Experts fear the fires are presenting an increased risk to homes and health given more appear to be burning near urban areas than in remote countryside.Wildfires have impacted London, Greater Manchester, North Yorkshire, County Durham, East Sussex, West Sussex, Devon and Somerset in recent days.Claire Belcher, director of the Wildfire Lab at the University of Exeter, said the latest firewave in England and Wales was the 'most widespread that the UK has seen'.She said climate change is causing wet winters leading to more vegetation growth which is then dried by long heatwaves, adding: 'We've had lots of fires in certain regions before, but we've never seen fires burning right across the country like this.'Ms Belcher also said: 'We must manage our land better to reduce risks and stop fires spreading. The impact of wildfires on wildlife can be devastating.'The term 'firewave' was coined by Imperial College London researchers last year and describes multiple urban wildfires triggered by extended hot and dry weather.It comes as parts of south-east England are on course to have no rain for nearly a month, with Wisley in Surrey having already experienced 26 consecutive dry days.