flames up to 35ft high engulfed 70 hectres of the st catherine 's hill nature reserve in christchurch , dorset .
a lack of rain combined with strong 45mph winds saw the blaze spread across the heathland dangerously quickly .
more than 80 firefighters spent six hours tackling the blaze which is thought to have wiped out thousands of animals .
dorset police confirmed they are treating it as suspicious after evidence of three deliberate fires was discovered .