I'd say the Challenger 2, because it's main gun has an 8km range and because of this:
Like every British tank since the Centurion, Challenger 2 contains a boiling vessel (BV) also known as a kettle or "bivvie" for water which can be used to brew tea, produce other hot beverages and heat "boil-in-the-bag" meals contained in ration packs.
That's right, you'd can be safely tucked up inside your Challenger tank, engaging the enemy from 8km away whilst sipping tea and eating Pot-Noodles.
A tank battle in a Challenger needn't be any more stressful than a weekend's camping.