Leicestershire's nine o'clock horses

My latest Joy of Six includes a piece by Francis Young on Britain's Christmas hobby horse customs, and I have seen other references to the Mari Lwyd and hoodening over the holiday.

All this has put me in mind of Leicester's nine o'clock horses. Roy Palmer writes about in his excellent Folklore of Leicestershire and Rutland in the context of the bogey man and other threats used by parents to keep their children in line:

By far the most widely-used threat was that of the nine o'clock horses which would mangle children who were out late, or even staying up too late. In some places they were called bell horses, which might indicate that the fear was originally connected with the curfew bell, which once rang at nine o'clock.

Most imagined them as real horses, ridden by Cossack-like horsemen. One child associated them with the horses that pulled the night-soil carts. Another heard the screams of their victims, but later realised he had been hearing train whistles.

Mr Ken Bell of Burbage remembers lingering at play one summer's evening early in the twentieth century, to the fury of his mother, who shouted: "I'll give you the nine o'clock horses". At that very moment the horse-drawn fire brigade came galloping through the village, and young Ken was in bed and under the blankets before the last hoof beats had died away.

The nine o'clock horses have been discussed by both the Leicester Mercury and the city's technology museum at Abbey Pumping Station. 

Both articles attribute these stories to the horse-drawn night-soil carts that took human waste out to the countryside for use as fertiliser. They say these carts weren't allowed into the city before nine in the evening, and add a story about children being stolen from there to work as farm labourers.

I'd like to see the evidence before I accept this explanation, which in any case does not account for the nine o'clock horses being familiar to children in Burbage, a village 15 miles from Leicester.

Later. There's a paragraph about the emptying of pail closets in the Victoria Country History of Leicestereshire. No mention of nine o'clock - and wouldn't you need daylight for such work? - and it seems that after the first couple of years the council did the emptying itself:

In 1871 the corporation decided to introduce the pail-closet system, which had been successful in various northern towns, and some 7,000 pail-closets were eventually installed. This development certainly did much to relieve the defective sewers, but difficulties arose in the removal and disposal of the night soil. At first, up to 1873, this had been removed by contractors, but the system proved unsatisfactory, and the task was then undertaken directly by the local authority although it proved to be very expensive. The night soil was loaded upon railway wagons in a siding in Freak's Ground, but the nuisance caused by this led in 1878 to legal proceedings against the corporation. Subsequently the sewage was loaded on to canal barges but this caused complaints that the canal was being polluted. The pail-closets were in fact never a satisfactory substitute for an adequate sewage system.