This man is believed to have raided his third Eastbourne betting shop today.
Ladbrokes is offering a £10,000 reward for information leading to his arrest and conviction.
He is pictured on CCTV at Ladbrokes in Seaside, Eastbourne, where hundreds of pounds were stolen in a gunpoint raid shortly before 9.30am today.
Police believe he was responsible for raids in Eastbourne on December 3 and December 20.
In today's robbery, a man carrying what looked like a gun in a plastic bag demanded cash from the cashier.
No shots were fired and nobody was hurt.
Detective Inspector Ian Williams said; "We believe that the same man is responsible for the two previous Ladbrokes robberies in Eastbourne, on December 3 and 20, 2012.
"He is described as a black man as depicted in the photograph, about 5ft 9in to 5ft 10in tall.
"If you were in the Seaside area this morning and saw this man entering or leaving Ladbrokes, or elsewhere nearby, or recognise the man in the photograph please let us know as soon as possible."
Anyone with information is asked to call Sussex Police on 101, quoting Operation Wootton, or Crimestoppers anonymously on 0800 555111.
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