social event for 40 people

[normy]

I have been asked to organise a corporate social in central london for around 40 people in August.
It has to involve some activity, food and drink, but be done on a shoestring budget (isn't it always the way!!)
I've got the obvious ones like playing rounders / softball in Hyde park, with a picnic, does anybody have any other ideas, and what food could i do?

[lafrancaise]

I plan these every year and have learnt you must have a back up of a room in case of rain and therefore need inside games planned just in case. We tend to go for picnics so you could do the finger meals of sausage rolls, scotch eggs, vegetable dips, fruit but make sure the food is kept cool in ice-boxes. One thing which is quite good is a trail where you pick up information as you do it and which brings everyone to the 'picnic' place. All depends who your 'people' are as to the kind of trail you do (architecture, shops, history) and you can make the clues funny or as riddles or anything you want. Hope this helps.