Matthew Holmes introduced his Class P in two batches of 6 engines.  The first batch was delivered from the NBR works at Cowlairs in 1886 and numbered 586-591

The second batch of 6 was delivered in 1889 and numbered 90-95.

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They bore a very close resemblance to their Drumond Class P predecessors in rebuilt form, (LNER class G8.)  The Drumond class P were the precursor to a long line of Scottish and English 0-4-4T classes. 

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Rebuilding took place between 1911-1913 under the tenure of W P Reid as CME of the NBR.  The rebuilding was in the form of fitting a redesigned boiler, this took place concurrently with the Holmes 17" x 24" goods engines  (LNER Class J33)  No's 91 and 588 were noteworthy because they still carried the safety valves on the dome.  These two also retained their toolbox at the rear of the bunker.  The other 10 engines had boilers with a conventional dome and had the engine toolbox removed from the footplate.  All the class had the tallow cup lubricators removed from the front of the smokebox to the side of the smokebox.

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In April 1913 No's 90 and 590 were fitted with vacuum ejectors. By 1920 No's 92, 587/89 had also received vacuum equipment.  The other six engines that weren't dual fitted with vacuum equipment at Grouping had that equipment fitted by the LNER between May 1924 and March 1926.  No. 9095 was the last of the class to be fitted with a vacuum ejector

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Until W.P. Reid introduced his 0-4-4T and 4-4-2T classes the class G7 worked on Glasgow local services.  Two engines were shedded at St. Margaret's to handle the North Berwick services.  In later NBR days the class was quite widely distributed.  The last one stationed in the city of Glasgow was No. 588. No. 590 was shedded at Eastfield for the Fort Augustus branch. No. 586 was at Kipps for the Slamanan line to Bo'ness.  No. 591 from Stirling was used on the Forth - Clyde Railway. 

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No. 93 was shedded at Carlisle for Langholm and St. Boswells services. No. 90 handled the Kelso to Dunfermline services. No.589 worked the North of Fife line and Dundee. No. 587 handled the St. Andrews services. Nos. 92 and 94 were at Perth.

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After Grouping a number of changes took place but their duties remained the same. No. 9588 worked the Roxburgh to Jedburgh Branch, No. 9095 Alloa to Alva.  Polmont - Bo'ness to Grangemouth was worked by No. 9092.

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Withdrawals began in August 1926 with No. 9587.  Six of the class were withdrawn in 1926-27.  There was a lull in the withdrawals until 1930 when a further 3 engines cut up for scrap at Cowlairs.  1931 saw another two go to the cutters torch leaving No. 9091 to soldier on until May 1932 on the Thornton-Methil Branch.