It appears that Harold may have been in the 25th prior to WW1, as he does not appear in other records such as the WW1 MEDAL cards, nor the 25th Londons address book.

National Army Museum Catalogue

• NAM. 1999-10-75 - 1
  Portrait photograph of Bugler Harold George Collins, 25th (County of London) (Cyclists) Bn The London Regiment, 1907.

• NAM. 1999-10-75 - 2
  Group photograph of four sergeants, two with cycles, 1911 (c); relating to Bug Harold George Collins, 25th (County of London) (Cyclists) Bn, The London Regiment.

• NAM. 1999-10-75 - 3
  Photograph of the 25th (County of London) (Cyclists) Bn, The London Regiment on parade with cycles, Rye Camp, 1911; relating to Harold George Collins, 25th (County of London) (Cyclists) Bn, The London Regiment.

• NAM. 1999-10-75 - 4
  Formal group photograph showing soldiers of the 25th (County of London) (Cyclists) Bn, The London Regiment at Rye Camp on mobilisation, 1914; relating to Harold George Collins, 25th (County of London) (Cyclists) Bn, The London Regiment.