A mother-of-two died after jumping "without hesitation" from the Dartford bridge, an inquest heard.
College lecturer Ann Harvey was seen by a crossing patrol officer to abandon her Citroen at the highest point of the Queen Elizabeth II Bridge, climb over two barriers and onto a recycling bin before jumping into the river below.
The officer later told police: "She made no hesitation in jumping."
Notes to her partner, children and mother were later found at her home in Westcliff-on-Sea, Essex, and Southend College where she worked in the art department.
The inquest at Gravesend's Old Town Hall was also told Ms Harvey had previously warned she would throw herself off the bridge.
A search for the 52-year-old was launched within minutes of her jumping just after 8pm on February 28 and involved the RNLI, Kent Fire and Rescue Service and police helicopter.
However, Ms Harvey's body was spotted on the foreshore by a resident of Ingress Park in Greenhithe and members of the public assisted the emergency services in attempts to resuscitate her.
Cause of death was given as partial transection of the aorta, a condition in which the largest artery in the body is torn or ruptured due to trauma.
North West Kent coroner Roger Hatch concluded that death was due to suicide.
Det Sgt Pauline Collins said Ms Harvey was last seen by her partner at about 5pm and told her she was going to Tesco for "food and a couple of beers".
However, there were no concerns when she did not return and it was assumed Ms Harvey, who had been diagnosed with mild bipolar, had gone to see friends.
DS Collins said: "There was nothing unusual about her behaviour...her partner wasn't unduly concerned."
The inquest heard that her two children, both in their twenties, had also been in regular contact with their mum and had not noticed a change.
The details of the notes left by Ms Harvey were said to be "too personal" and were not disclosed.
She had worked at the college since 2005 and was described as well-liked, very professional, diligent, conscientious and passionate.
DS Collins added that Ms Harvey had been suffering from depression and all the evidence pointed to her taking her own life.
"Suicide notes had been written and she had previously told her partner she was going to throw herself off the Dartford bridge."
If you would like confidential support on an emotional issue, call Samaritans on 08457 90 90 90 at any time.