NHER 13533 (Monument record) - Middle Level Main Drain

Constructed in 1843 to continue the Sixteen Foot Drain in Cambridgeshire to the Ouse at TF 5910 1476.
The northern end of this drain is interesting. It has two courses, one that loops to the south and passes under a disused sluice and bridge dated 1877; this section is now almost choked up. The straight line has a sluice dated 1934 and St Mary's Bridge is dated 1941. Yet the straight line is shown on the First Edition one inch Ordnance Survey map (original 1838, updated in about 1860). It appears that the 1843 alignment was abandoned here in 1877 and reinstated in 1934, unless the 1877 cut was intended to ease the pressure of water on the original sluice.
E. Rose (NLA), 8 July 1996.

The situation is explained by (S1). The straight line is the original, a sluice being made at the Great Ouse in 1848, replaced by an unusual syphon sluice in 1862; the diversionary sluice to the south is stated to date from 1880 despite the bridge date of 1877 (was it completed in 1880?) but in 1934 the new pumping station re-established the old course.
E. Rose (NLA), 21 December 2002.