Postman’s Park is one of my favourite London spaces. It is  poignant and quietly beautiful green space in the City of London, located just north of St Paul’s Cathedral between King Edward Street and Little Britain.
Established in 1880 on the site of former churchyards, it is named for the postal workers of the old General Post Office headquarters who often ate their lunch there during breaks.
The park was created from the merged burial grounds of St Botolph’s Aldersgate, Christ Church Greyfriars, and St Leonard, Foster Lane, reflecting the Victorian era’s efforts to reclaim disused churchyards as public gardens. Because of centuries of burials, the park sits slightly elevated above surrounding streets — a result of layers of soil laid over graves.
The Watts Memorial to Heroic Self-Sacrifice
The park’s defining feature is the Memorial to Heroic Self-Sacrifice, conceived by the artist George Frederic Watts and unveiled in 1900. It consists of 54 ceramic tablets inscribed with the names and deeds of ordinary men, women, and children who lost their lives saving others — people otherwise likely to be forgotten by history.
 
Interesting fact....
One of the most famous tablets is Alice Ayres, who saved children from a fire; her name inspired a scene in the film Closer (2004). it's worth a watch.