Short answers, pulled from the story.
William Fothergill Cooke and Charles Wheatstone developed and patented their telegraph system in May 1837. The Great Western Railway installed a five-needle version from Paddington station to West Drayton in 1838, making it the world's first commercial telegraph.
The inland telegraph was nationalised on the 1st of January 1870 under the Telegraph Act 1868. The total cost was £5.9 million, far exceeding Frank Ives Scudamore's original estimate of £2.5 million; by 1876, combined acquisition and extension costs had exceeded £10 million.
Gutta-percha, a natural latex from trees of the genus Palaquium in the Far East, provided the insulation that made submarine cables viable. William Montgomerie sent samples to the Royal Society in 1843, and the Gutta Percha Company, founded in 1845, held a near-monopoly on submarine cable cores in the United Kingdom until 1865.
John Pender created the Telegraph Construction and Maintenance Company in 1864 by merging the Gutta Percha Company with Glass, Elliot and Company. He founded a chain of companies that laid submarine cables connecting Britain to India, Australia, and other parts of the empire; these were merged as the Eastern Telegraph Company in 1872.
British Telecom ended the inland telegram service in 1982. International telegrams could still be sent by telephone after that date and were delivered by ordinary letter post.
The All Red Line was a worldwide telegraph network inaugurated in October 1902, comprising some 100,000 miles of undersea cables routed entirely through British territory. The name came from the convention of colouring British territories red or pink on maps of the era.