Work began this week on a £20 million project to rebuild the accident & emergency department at St Thomas' Hospital.
Construction work will continue for the next two years while A&E and all other services remain open as normal.
The scheme will create an emergency floor on the ground floor of Lambeth Wing and East Wing at St Thomas' Hospital to improve the care of emergency patients.
It will transform not only the A&E department but also the acute medical wards which patients are admitted to from A&E when they need hospital treatment.
Dr John Criddle, consultant in paediatric emergency medicine and clinical lead for the project, says: "We are redesigning our A&E and acute admitting wards to create a new emergency floor at St Thomas'.
"We will be relocating our acute medical wards, Sarah Swift and Victoria, to the ground floor of the hospital so they are nearer to A&E.
"Our plans also include a larger urgent care centre and a completely refurbished A&E department with improved facilities for all patients requiring emergency treatment."
Dr Simon Eccles, consultant in emergency medicine who is leading work to transform the emergency care pathway at St Thomas', added: "Our current A&E is simply too small – we treat an average of 380 patients a day and the department was designed to see a maximum of 300 patients a day.
"So patients will see a real difference in terms of an improved environment for their care.
"It is a major challenge because the new A&E will be built while the existing department is still very much open 24 hours a day. It will be a bit like changing the wheels on a car without stopping!"