Grand Theft Auto: London 1969 has no in-game completion percentage and no reward for doing everything: progress is a target score per chapter, and the game counts each chapter's Kill Frenzies as "secrets". This checklist follows the community 100% definition (gta.wiki): in each of the four chapters, reach the target score and complete every mission and every Kill Frenzy.
Totals (63 objectives): 39 missions on PC (38 on PlayStation: James Bomb is PC only), 21 Kill Frenzies and 3 score targets (Boys will be Thieves has none).
How the percentages work: since there is no official split, each chapter weighs its share of the required objectives (Boys will be Thieves 1.59%, Mods and Sods 33.33%, Chelsea Smile 31.75%, Dead Certainty 33.33%).
Chapter endings are unlocked by the target score and are not listed separately. Every mission can be attempted only once per playthrough of a chapter. The PC version is a mission pack that needs Grand Theft Auto installed.

