BBC news reports that sheep have learned methods to bypass controls:

Hungry sheep on the Yorkshire moors have taught themselves to roll 8ft (3m) across hoof-proof metal cattle grids – and raid villagers’ valley gardens.

The crafty animals have also perfected the skill of hurdling 5ft (1.5m) fences and squeezing through 8in (20cm) gaps.

That sounds like baaaad security. :) Time for a redesign.

May I humbly suggest RFID tags for the sheep with wireless detection around the gardens?

Although tagging with wireless has more serious privacy and economic implications (no more hiding sheep during inventory/tax season) it is less unsightly. Aesthetics seem important to me when thinking about the English countryside.

Dogs might also be a good control addition. Where are Wallace & Gromit when you need them?