I found this extract from the 1828 printing of ‘City Scenes’ by William Darton

Well, here is the Bellman and Crier, calling the attention of the people to a description of a child that has been lost.  The number of children who have at times been stolen from their homes, has caused great alarm to many parents.  It was not far from London Bridge that little Tommy Dellow was taken away, which caused the parish-officers to advertise a reward of one hundred guineas for his recovery; and the bills were the means of his being discovered at Gosport, in Hampshire.  It appeared that this little boy and his sister were enticed away by a decentlydressed woman, who sent the girl home, but took the boy.  Having no children of her own, she contrived to take him to Gosport, and to present him to her husband, on his return from a long voyage at sea, as his own son.  The whole history of the distressing loss and happy recovery of little Thomas Dellow, has been published; and, in another account of him it is shortly described in verse.

The little boy and girl, who stand hand in hand, before the man with the basket on his head, are the portraits drawn from the life of little Thomas Dellow and his sister.

 “A sweet chubby fellow,
Named little Tom Dellow,
His mamma to a neighbour did send,
With a caution to stop
At a green-grocer’s shop,
While she went to visit a friend.

“The poor little soul,
Unused to control,
O’er the threshold just happen’d to stray,
When a sly cunning dame,
Mary Magnay by name,
Enticed the young truant away.

“At a pastry-cook’s shop
She made a short stop,
And gave him two buns and a tart,
And soon after that
She bought him a hat
And feather, that made him quite smart.

“Then a man they employ
To describe the sweet boy,
Whom they sought with such tender regard!
And soon you might meet
Bills in every street,
Which offer’d five guineas reward!

“They did not succeed
To discover the deed,
Tho’ much all who heard of it wonder’d,
Till at length they sent down
Large bills to each town,
And raised the reward to one hundred!

The office of bellman was first instituted in 1556, for the purpose of going round the ward by night to ring his bell, and to exhort the inhabitants, with a loud voice, to take care of their fires and lights, to help the poor, and pray for the dead.  This custom, though once general, is used only at Christmas-time, when a copy of verses is repeated, instead of the admonition used in former days.