The final stage of the scheme involves replacing the remaining green copper roof covering the nave and will be the largest part of the restoration.
The scaffolding required is even more complex than before and will take around five months to build.
Work to replace the cathedral’s failing copper roof – which was installed after World War Two, when the traditional material lead was in short supply – first began in 2018.
The copper roof had been allowing rainwater to penetrate the roof vault, damaging the medieval timber structure, masonry and ceiling plasterwork.
The second phase of the five-year project was completed at the end of last year, when the huge scaffolding hugging the building was removed to reveal the new grey lead roof, providing a striking visual contrast with the remaining green copper covering the nave.
This phase included masonry works to repair nineteenth century stones on the lantern – the central tower beneath the spire.
Decorative stone pillars and stone blocks that face the salty south-westerly coastal wind had become badly eroded and have now been restored.
The copper removed so far has been recycled, with one section being transformed into an angel sculpture by Chichester University student Helen Solly.
Work on the third stage of the project has been deliberately delayed in order to safeguard the peregrine falcons which return each spring to breed on the spire, as it can only proceed during their nesting season from March to July if the scaffolding and temporary roof are complete, and entirely wrapped to hide the human activity.
Work will commence on the nave roof in the summer of 2020 to complete the project once any peregrine chicks have fledged.
The Chichester Cathedral Trust is fundraising for the remaining £1.7 million needed to complete the project.
The cathedral receives no automatic statutory funding, relying on donations, fundraising and self-generated income.
The Dean of Chichester, The Very Reverend Stephen Waine, said: “Chichester Cathedral has been sacred place of Christian worship for over 900 years...
“The High Roofs Project is vital in protecting the cathedral’s future for all.”