Roy Sinclair threatened the High Street employee with a knife, before helping himself to money from a till, in February 2022.
The 43-year-old, of Otterden Street, Sydenham, handed himself in to Kent Police two days later and went on to admit robbery and possessing an offensive weapon in a public place.
He was sentenced at Maidstone Crown Court on Monday 25 April 2022 and will be the subject of a two-year extended licence when he is eventually released from prison.
Sinclair entered Lloyds Bank at around 3pm on Friday 4 February and was seen by members of staff walking around the premises with no apparent purpose.
When a cashier called to offer help, he walked behind their counter, pulled out a knife, and held it close to their body. He then demanded money and said ‘no alarms or I’ll kill you.’
The victim opened their till and Sinclair helped himself to cash before leaving the scene on foot. The cash taken consisted of discontinued £20 bank notes.
Two days later, he phoned Kent Police and confessed to the offence during a conversation with a call handler.
Officers were subsequently dispatched to detain him and he has been held on remand since.
The hooded jumper he was wearing at the time of his arrest matched what he wore on the date of the offence. A pair of green jogging bottoms, which were worn when the robbery was committed, were also found at his home address.
Police Constable Emma Laimbeer, Kent Police’s investigating officer for the case, said: ‘The victim of this case had every good reason to believe their life was in danger and I am pleased we have now secured justice for them.
‘Although Sinclair admitted the offence, it does not in any way undo the harm he has caused and the only proportionate outcome is for him to receive this custodial sentence.
‘We will never show any tolerance towards anyone who chooses to use violence against innocent members of the public.’