An investigation into an armed robbery at a Norwich bookmakers just 24 hours before a second robbery at a supermarket petrol station has been closed after police said all lines of enquiry have been 'exhausted'.

One of the men who raided Betfred bookmakers in Hall Road at about 9.30pm on June 1 was armed with a shotgun or replica shotgun, while the other had a large metal pole. Both men were wearing balaclavas and threatened two members of staff along with a customer.

It was linked to a second robbery at the Asda petrol station on Boundary Road at about 4pm on June 2 when suspects demanded cash from two workers.

A police spokseman said: "Following an extensive investigation, the case has been closed due to that fact that all lines of enquiry have been exhausted. This includes forensics, CCTV and witness accounts. However, should further information come forward we would always review this."