At the Council meeting held in October 1936, it was resolved to ask that a foundation stone be laid, if possible by a member of the Royal Family, during the summer session of the Church Assembly the following year. The Secretary reported that the Archbishop of Canterbury, Dr Cosmo Lang (Archbishop 1928-1942), was of the opinion that His Majesty King Edward VIII would be unable to undertake engagements of this nature in the months succeeding his Coronation. His Grace was, however, prepared to invite Her Majesty Queen Mary to lay such a stone.
The following month the Secretary wrote to Dr Lang asking for permission to release to the press the news that a member of the Royal Family was associated with the new building. 'Your Grace will remember that it is desirable that it should be so made because the newspapers will then be very careful not to allow adverse criticism to be published.'
The date was later fixed for 26 June 1937 and Dr Lang arranged with Sir John Reith to have the ceremony broadcast by the BBC. The afternoon, so some said, could have been better planned. Perhaps use might have been made of some of the stands left over from King George VI's Coronation. Instead, before Queen Mary arrived, invited guests were kept standing for more than an hour, penned in like cattle between the iron railings of Dean's Yard and a raised platform which, occupied by the dignitaries, obscured the view. 'The singing of the hymn, 'Praise, my soul, the King of Heaven' was sadly bungled', according to the Church Times, and the band which, the Guardian added, 'had discoursed Gilbert and Sullivan before the ceremony, found themselves at sea when they accompanied the hymn, for the assembly knew the tune too well to take the beat from the band, which had to struggle manfully to follow the singers.'
With the master mason in shirt sleeves at her side, Queen Mary, dressed in white suede crepe, then stepped forward. Listeners all over Britain and America, but not those standing in Dean's Yard, heard Her Majesty's words as she spread cement along the block with a silver trowel and, with a wooden mallet, performed the ceremony: 'in the Faith of Jesus Christ we lay this stone in the name of the Father and of the Son and of the Holy Ghost.' The architect later noted that the steel framework of the dome was like a red crown over the whole proceedings.
The trowel and the mallet, the latter fashioned from the timber excavated during demolition of one of the fourteenth-century oak piles to which barges were once moored, were afterwards handed back to the Corporation. (These items are displayed in the Entrance Hall during Centenary Year.)
After his address, the Archbishop 'called for three cheers for Queen Mary, which were given with great enthusiasm to the waving of top hats and handkerchiefs.' Her Majesty then walked round to the Jerusalem Chamber, where she took tea with the Dean of Westminster.