FREE 300-degree views of London from H22 (58th floor), followed by Parks & Bridges walk.
Horizon 22 (Bishopsgate) is London's highest free viewing platform on Level 58 (254 metres). There are lifts. ["Small size backpacks and bags are fine and will need to pass through security screening on arrival" - see website link for FAQs].
UPDATE Wed 28th - we have 30 places booked, but 40 who are hoping to come - Horizon 22 do have limited casual walk-up entry, but a wait may be involved. Given these numbers, bringing sandwiches for lunch would be a good idea.