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Grade I listed. Link
St Augustine, Watling Street was an Anglican church formerly located just to the east of St Paul's Cathedral in the City of London. It was destroyed in the Second World War but its remains now form part of St Paul's Cathedral Choir School.
Wikipedia: Link

Sir Christopher Wren was Commissioned with rebuilding a number of the Churches destroyed in the City of London, by the Great Fire of London. His office rebuilt 51 churches, not all survive.
See Link for a list of churches.
Google map of their location: Link

Grade I listed buildings and structures are of exceptional, even international importance. There are over 6,000 in the country. Only 2.5% of listed buildings are Grade I listed.
In Scotland the classification is Category A
Index: Link

St Paul's Cathedral is the Anglican cathedral on Ludgate Hill in the City of London and the seat of the Bishop of London. The present building dates from the 17th century.

It was designed by Sir Christopher Wren with the first stone of the cathedral laid in 1677.

Link