William Taylor was last seen at his home in Gosmore at around 9pm on Sunday, June 3. It was his 70th birthday on Monday (June 11).
His son Richard Taylor has made said: “If anyone out there knows anything about my dad’s whereabouts please contact the police.
"This is an unbearable situation and I am worried sick about him. My family is in turmoil and we are desperate to get him home.”
DI Mike Keane, from the North Herts Local Crime Unit, said: “We are carrying out extensive enquiries to find William Taylor.
"His family are incredibly worried and I am appealing to anyone who might have seen William or has information on his whereabouts to get in touch. We’re growing increasingly concerned for his welfare, so any information you have, no matter how small it might seem, could be vital in us finding William.
“William is described as white, around 5ft 11in tall, of medium build with short grey hair. He was last seen wearing a baby blue-coloured shirt, jeans and black wellies. William may be wearing a navy blue boiler suit."
If you have seen him since he went missing or have information about his whereabouts please contact Hertfordshire Constabulary via the non-emergency number 101.
If you believe you are with William or have seen him in the last few moments please call 999.