The soldier in the full-length study was, undoubtedly, a member of the British Infantry - The Leicestershire Regiment. The large 'Royal' tiger which formed the centre of that Regiments badge is quite plain to see for those of us familiar with such adornments. He carries a 'swagger' stick under his right arm - 'a bit of show' which, prior to WW2, soldiers added to their dress when 'walking out,' (maybe to impress the ladies - although they'd maybe need to try a bit harder than that nowadays!).
The sticks, (of cane or similar, pliable material,) usually, also bore the regimental badge embossed on a white metal or sometimes even silver, top - just visible in this photo forward of the young man's fingers of his right hand. They also had metal tips - often brass. It may be of interest to note that in British cavalry regiments, the soldiers carried whips instead. 'Swagger Sticks' should not be confused with officers' canes which were generally thicker, leather covered, devoid of metal fittings and barely pliable - as carried by Dad's Army's Capt. Mainwearing!
Although the more modern, 'webbing' (material) equipment had been in existence since 1908, the chap in The Leicesters wears what is referred to as a '1914 Pattern Leather Equipment' belt with what those of us of older generations will recognize as a 'snake' hook fitting. Accoutrements in both materials existing, side by side, for some time until leather eventually phased out.