NHS staff, patients, firefighters and local dignitaries gathered in the gardens of St Thomas' Hospital on Thursday to mark the 75th anniversary of the first bomb to fall on the hospital during the Blitz.
At the end of Thursday's service, 12 roses were placed in front of the fountain which now occupies the site of one of the bombed buildings to represent each of the victims.
The Bishop of Southwark, Rt Revd Christopher Chessun, gave the blessing.
Firefighters from Lambeth Fire Station attended the service in recognition of the sacrifice made by the two auxiliary firemen.
The Mayor of Lambeth, Cllr Donatus Anyanwu, was also in attendance.
"The Blitz was a significant period in the history of Guy's and St Thomas', and the history of London," said Sir Hugh Taylor, chairman of Guy's and St Thomas' NHS Foundation Trust.
"Staff at the hospitals did their best for their patients in terrible conditions, sometimes even sterilising their equipment on Primus stoves so that they could work in the converted basement wards when the hot water wasn't running.
"The first bombs hit the hospitals on 8 and 9 September 1940. Now, 75 years on, we remember the doctors, nurses and physiotherapists who died at St Thomas' during the Blitz."
On Thursday evening a minute's silence was kept at the Guy's and St Thomas' NHS Foundation Trust annual public meeting to remember those killed in the Blitz.
"The Florence Nightingale Museum stands today on the site of the nurses' home that was destroyed 75 years ago, and four nurses lost their lives, said Natasha McEnroe, director of the Florence Nightingale Museum.
"This is an important anniversary as it marks the heroism of medical staff during wartime who put the safety of the patients before their own."
Hospital chaplain Revd Mia Hilborn added: "In this anniversary year, we remember the courage and bravery of so many at Guy's and St Thomas' hospitals during the war years."
Dr J C Campbell (House Surgeon)
Miss Doucet (Physiotherapist)
Mss S Dunn (Physiotherapist)
Miss S Durham (Physiotherapist)
Miss K M Forbes (Student Nurse)
Miss G Lockyer (Physiotherapist)
Miss H M Richardson (Nursing Auxiliary)
Dr P B Spilsbury (House Surgeon)
Miss B Mortimer-Thomas (Physiotherapist)
Miss C G Walker (Student Nurse)
Robert Tanner (Auxiliary Firefighter)
Evan Morgan Jones (Auxiliary Firefighter)