Locks: Grand Union Canal South 27 - 52

 Grand Union Main Line Southern section, locks 27 - 52:  Soulbury to Berkhamstead

The Grand Union Canal Main Line runs for 137 miles through 166 locks from Brentford on the River Thames to Salford Junction in the north east of Birmingham. All the locks are double width locks except the final 11 locks in Birmingham. The locks on the Knowle flight are the first double width locks heading south from Birmingham.

The southern section runs from Brentford in London 93 ½ miles through 101 locks to Braunston. The southern section of the Main Line was originally built as the Grand Junction canal. The Grand Junction canal opened from Braunston to Weedon on 21st June 1796, and a few weeks later it was extended as far south as Blisworth, where a long tunnel was under construction. Blisworth Tunnel and an embankment at Wolverton were not finished until March and August 1805 when the Grand Junction was opened as a through route for the first time. In the meantime goods had to bypass Blisworth Tunnel on a temporary railway, and at Wolverton a diversion via the river Ouse was required.

The Grand Union Canal was formed in 1929 from many separate canal systems. The Main Line itself was formed from the following four canals:

- Birmingham & Warwick Junction Canal (Salford to Bordesley)
- Warwick & Birmingham Canal (Bordesely to Warwick)
- Warwick & Napton Canal (Warwick to Napton)
- Grand Junction Canal (Brentford to Braunston)

There is a five mile section from Braunston to Napton which is actually the Oxford canal. This section was never bought by the Grand Union Canal Company.

The Southern Main Line locks are numbered from 1 at Braunston at the northern end to 101 at Brentford at the southern end.

Lock 27 - Leighton lock (6' 8")

Lock 28 Grove lock (7' 6")

Lock 29 - Church lock (6' 9")

Lock 30 - Slapton lock (7' 1")

Lock 31 - Horton lock (6' 9")

Lock 32 & 33 - Ivinghoe locks (14' 3")

Lock 32 - Ivinghoe Bottom lock

Lock 33 - Ivinghoe Top lock

Lock 34 - 36 - Seabrook locks (20' 4")

Lock 34 - Seabrook Bottom lock

Lock 35 - Seabrook Middle lock

Lock 36 - Seabrook Top lock

Lock 37 & 38 - Marsworth Lower locks (14' 4")

Lock 37 - Bottom lock

Lock 38 - Top lock

Lock 39 - 45 - Marsworth Upper locks (42' 3")

Lock 39 - Bottom lock

Lock 39 - Bottom lock

Lock 39 - Bottom lock

Lock 40

Lock 40

Lock 41

Lock 42

Lock 43

Lock 44

Lock 45 - Top lock

Lock 45 - Top lock

Lock 46 - Cowroast lock (6' 0")

Locks 47 & 48 - Dudswell locks (13' 4")

Lock 47 - Dudswell Upper lock

Lock 48 - Dudswell Lower lock

Lock 49 - 52 - Northchurch locks (26' 11")

Lock 49 Northchurch lock

Lock 49 Northchurch lock

Lock 50 - Bushes lock

Lock 51 - Gas 1 lock

Lock 52 - Gas 2 lock