Cassiobury Farm and Fishery Open Days have been running throughout the summer, the last is are Saturday 31st August.
You can either order on-line (by scrolling down to the day you wish to visit them on, by clicking on the following link) http://www.cassioburyfarm.co.uk/open-days-events/ or simply by purchasing tickets at the gate on the day.
They accept cash and credit cards on the gate. Prices are the same whether ordered on-line or at the gate, but there is a fast track entrance for those with on-line tickets so access is quicker.
Access to the Farm is on-foot only. The Cassiobury Park website gives the best information for parking and public transport. http://cassioburypark.info/directions-to-cassiobury-park/
There is on-site parking for blue-badge disabled drivers. No pre-booking is necessary. Access the Farm via Rousebarn Lane (use postcode WD3 3GD). No dogs, other than guide dogs, are allowed on-site.
You can leave and return during the day if you wish. Just ask the gate to stamp your hand.
Gates open at 10:00am. Last entry is 4:00pm and the Farm closes at 5:00pm.