A man forced his way into the victim s house in Cedar Road while she was at home sometime between 7pm and 8pm yesterday, Monday February 1.
The suspect demanded money and jewellery and the woman was threatened with a knife, suffering a small cut to her arm.
Dc Rachel Martin, of Rayleigh CID, said: “The victim was extremely courageous and would not allow herself to be intimidated by him.
“She talked to him in an effort to keep the situation as calm as possible and when she saw her chance to escape, she told him that there was cash in the conservatory.
“She managed to lock him in and run out the front door to alert a neighbour.
The suspect managed to get out, leaving with a three figure sum of cash.
Police carried out a search of the area and house to house enquiries, and are continuing their search for the suspect. The victim was taken to hospital for a check-up and later discharged after treatment.
The suspect is described as white, of slim build, aged in his 20s and about 5ft 9ins tall. He wore a green scarf around his face, a black woollen hat, boots and gloves.
Dc Martin said: “This was a frightening ordeal and I am appealing for anyone who saw a man acting suspiciously in the area at the time and fitting the description to contact us urgently.
Witnesses or anyone with information can call Rayleigh CID on 101.
Alternatively, they can contact Crimestoppers anonymously on 0800 555111 or www.crimestoppers-uk.org.