London (CN/CP Junction)

The Buck Diamond is London's CN/CP crossing: the place where Canadian Pacific Kansas City's Galt Subdivision crosses the Guelph Subdivision at grade, in the city's east end near First Street and Dundas Street. The Guelph Subdivision is CN-owned and was long operated by the Goderich–Exeter Railway (GEXR); London railfan Railfandan's local guide describes the spot as the place "where the Canadian Pacific Galt subdivision and GEXR Guelph subdivisions cross each other", and shows VIA Rail train 84 rolling across the diamond on its way east.

First Street crosses the tracks on an overpass right beside the diamond, and Dundas Street crosses the lines about 250 m (800 ft) to the south, so the junction can be watched from public streets without going near the rails. Traffic is a mix of CPKC freight on the Galt Sub and VIA Rail and freight movements on the Guelph Sub; no published train count was found for this crossing.

Two other London locations in the same guide are worth combining with a visit: CP's Quebec Street Yard, reached by the Galt Subdivision closer to downtown, and CN's Egerton Street Yard on the Dundas Subdivision.

The junction sits on flat urban terrain in London's east end, roughly 250 metres above sea level. The surrounding neighbourhood is a mix of light industrial properties, residential streets, and commercial development. The most prominent landmark is 100 Kellogg Lane, the former Kellogg's cereal factory that operated from 1924 until its closure in December 2014. It has since been redeveloped into a sprawling entertainment complex housing indoor adventure parks, breweries, and event spaces—a useful amenity for railfans looking to combine a train-watching session with food and activities.

The Thames River valley lies just a few blocks to the south, with green corridors along the riverbanks providing contrast to the industrial rail corridor. Sight lines along the tracks are generally open, with no overhead wires—both CN and CPKC operate diesel traction on these lines. Winter brings clean contrast between dark locomotives and snow-covered rail infrastructure.

The soundscape is distinctly industrial: crossing bells, horn blasts at nearby road crossings, the metallic clatter of wheels on the diamond frogs, and the rhythmic clanking of couplers during yard switching operations.

London's importance as a railway junction dates to the 1850s, when the Great Western Railway completed its mainline through the city connecting Niagara Falls to Windsor via Hamilton in 1853-54. Grand Trunk Railway also reached London from St. Mary's, making the city a significant rail hub in Southwestern Ontario. The Great Western was eventually absorbed into Grand Trunk and ultimately became part of Canadian National Railways.

The CP presence in London traces to the London Junction Railway, incorporated in 1882 by local investors to connect the city with the Credit Valley Railway's expanding network to the south. In 1883, the Credit Valley Railway leased the London Junction line, and both were amalgamated into the Ontario and Quebec Railway on November 30, 1883. Canadian Pacific Railway absorbed the O&Q on January 4, 1884.

The adjacent Kellogg's cereal factory, built in 1924, operated for 90 years as one of London's defining industrial landmarks, producing up to 750,000 boxes of cereal daily at its peak and employing generations of local workers. The plant closed in December 2014 after an 89-year legacy, and the site has since been reimagined as 100 Kellogg Lane, a major entertainment and commercial complex.

A significant modern chapter was written with the opening of the $87.6 million Adelaide Street North underpass in April 2024, eliminating one of the city's most problematic railway-road conflicts.

The Buck Diamond is London's grade crossing between Canadian Pacific Kansas City and a CN-owned line, a type of junction that is becoming rare as railways grade-separate their crossings. VIA Rail trains between London, Kitchener and Toronto use the Guelph Subdivision across it, so passenger trains cross the diamond as well as freight. The redeveloped 100 Kellogg Lane complex, in the former Kellogg's cereal plant, is a short trip away for food and indoor activities.