Young people in Hanworth are being urged to be on their guard this week after a third "hammer" attack - which police believe to have been carried out by the killer of 19-year-old Marsha McDonnell.

They have been warned by police to be extra vigilant - and when walking home to be aware of who is behind them and to tell people where they are going.

The latest savage and seemingly motiveless assault was on an 18-year- old youth in Howard Close, just a brief walk from Hanworth's border with Hampton.

It occured in the early hours of Tuesday morning, just half a mile from where Marsha was found.

The hunt is on for a young man with a white hood and dark jacket with both hoods up to hide his face, who tried to bludgeon the teenager with what might have been a hammer or iron bar.

The victim's name is not being released, but he is known to live in the immediate vicinity and be a student at a Richmond college.

One theory being explored is that he might have been mistaken for a young women because it was dark and he is slightly built.

The attacker was described as between 5ft 10in and 6ft tall, wearing a white top and dark jacket with both hoods up, dark tracksuit bottoms and dark shoes. The youth could not see his skin colour,

Police are convinced he is living locally or familiar with the area.

Night patrols have been stepped up and police are thought to have mounted covert operations.

The records of psychiatrically disturbed people are being checked to see if they live in or have moved to the area.

Meanwhile, Richmond upon Thames College, which caters for hundreds of students from Hounslow, and has schooled both the most recent victim and Marsha, who left last year, has issued a warning to students.

A spokesman said: "In the circumstances, the college exhorts all students to exercise extreme care with regard to the potential danger associated with being out late at night, particularly unaccompanied."

Police were called at approximately 2.50am on February 25th by an 18 year old man who reported that whilst walking home someone had attempted to attack him.

The youth had been out for the evening in Kingston with friends and had taken the N285 night bus home.

He alighted in the Hampton Hill area and walked along the Uxbridge Road into Howard Close and on into Ormond Drive.

He heard a noise and turned to see a man jogging behind him. He tried to cross the road when the man swung at him with what is believed to have been a blunt instrument.

The man, missing him, swung at him again, this time just making contact with his waist, causing a very minor injury.

The man then ran off along Uxbridge Road and the victim phoned police from his mobile phone.

The incident is being investigated by DCI Richard Freeman and his team. They are now linking the attack with the murder of Marsha McDonnell on February 4th in Priory Road and the attack on a 17-year-old in Walpole Gardens, Strawberry Hill on January 8th.

Meanwhile the last two potential witnesses to Marsha's murder that police had been searching for - who were last seen getting off a bus at Hounslow's Treaty Centre have come forward.