About 80 Royal Marines from Alpha Company are due to land at RAF Brize Norton at about 2pm. They'll then be transported to Norton Manor Camp near Taunton by coach, greeting friends and family at around 6pm.
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It will be dry and bright in the morning but as the day goes on it will become wet and very windy.
Eastern parts will have heavy rain in the morning, clearing by afternoon.
Fire and Rescue Service says it received a 999 call to say there had been an explosion in a third floor flat within a mid terraced building.