A man who has been missing for more than one week is believed to have links to Cambridgeshire.
Oliver, who is from Stevenage, was last seen at around 4.45pm on Wednesday May 22).
The 27-year-old also has links to Cottenham in Cambridgeshire, said police.
An officer said they are now "growing increasingly concerned for Oliver's welfare".
Oliver is described as being of slim build and around 5ft 8in tall. He has shoulder-length, light brown mousey hair, blue eyes and is clean shaven.
He was last seen wearing a grey jumper, a black jacket, North Face grey joggers and grey trainers. Oliver was also carrying a black man bag.
If you believe you are with Oliver now or have seen him in the last few moments, you are asked to call 999 immediately.
If you have seen Oliver since he was reported missing or have information about where he has been, you are asked to report it at herts.police.uk/report, via web chat or by calling 101. You should quote ISR 540 of May 22.
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