Building on its experience in the design, development and production of the S52 (4 × 4) armoured patrol car and the S55 (4 × 4) armoured personnel carrier, both based on the Land Rover Defender 110 chassis, Short Brothers of Northern Ireland developed the S600 internal security vehicle (ISV) as a private venture.

While the earlier S 55 series meet the operational requirements of many army and police forces, some requirements now call for a vehicle with increased carrying capacity, more internal volume and improved cross-country mobility.

In 1992, Short Brothers started looking at existing chassis which could be used as the basis for a new ISV and finally selected the proven German Mercedes-Benz UNIMOG U1550L/U2150L (4 × 4) chassis.

Some 80 per cent of the components used in the S600 are standard commercial components, which have already demonstrated high reliability and a low maintenance requirement. In order to fit the armoured body, some parts of the UNIMOG chassis have been repositioned.

Detailed design work on the S600 started in 1993 and was completed in 1994, with the prototype being rolled out early in 1995.

The description is for the baseline S600 as there is considerable flexibility in the design of the S600, allowing it to be tailored to meet individual operational requirements.

When being used in the internal security role, for example, 14 (1 + 13) men can be carried while for the military role a section of eight men and three days' supplies can be carried.

As part of restructuring, in 1996 Short Brothers sold the completed design, development and production rights of the S600 series of vehicles to BAE Systems Australia.

This deal also included the Short Brothers Shorland S52 armoured patrol car and the S55 armoured personnel carrier, both based on a Long Wheelbase Land Rover (4 x 4) chassis.

No production of the S52 or S55 was even undertaken in Australia and for this reason details of these two vehicles, which remain in service with many countries, are given under the United Kingdom.

The first order for the S600 was placed by the Kuwait National Guard who in 1997 ordered 22 vehicles with production of these being undertaken in Australia and first deliveries being made in 1998.

In 1999 BAE Systems Australia acquired all of the vehicle business of BAE Systems Australia including the S600 product range.

In 2001 Tenix Defence Systems restarted production of its S600 Shorland (4 × 4) ISV for the Belgian Gendarmerie who placed an order valued at AUD5 million for an undisclosed quantity of vehicles, (which is believed to comprise six units).

The S600 Shorland (4 × 4) APC in the Internal Security Vehicle (ISV) configuration was selected by the Belgian Gendarmerie following extensive competitive trials alongside a number of other vehicles.

According to Tenix Defence Systems its S600 Shorland (4 × 4) was selected by the Belgian Gendarmerie as it met a number of key operational criteria including mobility, protection, obstacle clearance, through-life cost and supportability.

The ISV configuration of the S600 provides seating for up to 12 fully equipped personnel who can rapidly enter and leave the vehicle via the rear and/or sides of the vehicle.

Belgian vehicles are fitted with an air conditioning system, run-flat tyres, powered steering, powered sliding door, spotlights and wire-mesh protection for the windscreen and a rapidly removable front-mounted power-operated light obstacle removal device.

As previously stated, the S600 was originally offered based on the UNIMOG U1550L/U2150L (4 × 4) chassis but as of mid-2005 it was being offered based on the more recent and current production U-5000 (4 × 4) chassis.

According to the United Nations Arms Transfer List for 2005, Singapore took delivery of two S600 ISV in this period. These are understood to be fitted with the Mobile Adjustable Ramp System (MARS).

In January 2008 it was announced that BAE Systems had entered an agreement to acquire Tenix Defence Systems for up to AUD 775 million (GBP 356 million) in case. When this is confirmed Tenix Defence Systems will be integrated with the operations of BAE Systems Australia. Description

The hull of the S600 is of all-welded steel armour construction that provides all-round protection from 5.56 and 7.62 mm ball small arms fire. If required, appliqué armour can be added to provide a higher level of protection against 5.56 and 7.62 mm armour-piercing attack. Underneath protection is provided against grenade and small mine threats.

The engine and transmission are at the front of the vehicle with access to the Mercedes-Benz OM-924LA engine for maintenance purposes being through hatches. If required, the complete armoured body can be removed from the chassis to allow full access to the power pack.

The diesel engine is coupled to a manual transmission which gives a total of eight forward and four reverse gears. The portal axles have hub drive and torque tubes. Both axles have pneumatically operated differential locks, which can be operated while the vehicle is moving.

Suspension at each wheel station consists of coil springs and hydraulic shock-absorbers with steering being power assisted to reduce driver fatigue, especially when moving across rough country.

Both left- and right-hand drive models are available. In the case of the former, the driver is seated front left with the vehicle/detachment commander to his right. To their front and sides is a bulletproof windscreen that gives excellent visibility through 180°. The bulletproof windows provide the same level of protection as the hull.

The troops are seated on bench seats that run down either side of the hull facing each other with each person being provided with a seat belt. Space is provided under the seats for the stowage of equipment and stores.

To allow for the rapid entry and exit of the troops, which is considered essential for many of the roles that the S600 is expected to undertake, the S600 has three means of entry. In each side of the hull is a two-part hatch, the upper part with an integral vision block opens upwards while the lower part folds down to form a step.

In the rear of the hull is a similar but wider hatch with the upper part, which can contain a firing port and vision device, opening upwards and the lower part folding downwards to form a step. If required, the upper part can be locked in the open position while travelling. Other door configurations are available if required.

If the S600 is operating away from its base for extended periods, without extensive logistic support, a replacement wheel can be carried on either side of the hull towards the rear.

The prototype S600 had three bulletproof vision blocks in either side of the troop compartment, but again there is flexibility in the design and, if required, firing ports can also be fitted.

The prototype had a single-piece circular hatch cover in the roof and a wide range of armament systems up to and including a .50 (12.7 mm) M2 HB machine gun or a 40 mm MK 19 Mod 3 grenade launcher can be fitted.

Other roof hatch arrangements are possible on the S600, for example a circular roof hatch above commander's and driver's positions, standard circular roof hatch for machine gun (as on the prototype) and twin hatch covers at the rear.

Standard equipment on production vehicles normally includes an air conditioning system.

Optional equipment for the S600 includes appliqué armour, front-mounted self-recovery winch, wire cutters, smoke grenade launchers, land navigation system (such as a global positioning system), Mercedes-Benz central tyre-inflation system that allows the driver to adjust the tyre pressure from his position to suit the type of ground being crossed, Hutchinson run-flat inserts, automatic transmission, thermal image surveillance equipment, NBC system, driver assist camera for MARS (see below), powered sliding doors, additional fuel tanks, heater, fire detection and suppression system, night vision equipment and various communications systems. Variants

Tenix Defence Systems has suggested that the S600 could form the basis for a wide range of variants including:

This is also referred to as the S600 High Pressure Hose Vehicle (HPHV). The 3,000 litre water tank offers over five minutes of continuous waterjet operation or up to 15 minutes of pulsed operation.

The water cannon is mounted on the roof and is traversed and elevated by electric drive motors, with the operator controlling the cannon using a joystick on a hand-held control box from the safety of the cockpit.

The high-pressure pump is mounted securely under the body and the water tank is filled from a roof-mounted filling point or through a combined hydrant and drain valve.

At least one customer has purchased the S600 fitted with the Mobile Adjustable Ramp System (MARS), which can be used for rapid response for terrorist, hostage or emergency situations.

This would be fitted with a front-mounted heavy-duty self-clearing barricade removal blade.

Accommodating a crew of three including driver and two medical staff; it can carry three stretcher patients or two stretcher patients plus four seated patients.

Carrying a 81 mm mortar with a crew of three including driver, mortar detachment commander and mortar crew member. This would fire through an opening roof hatch.

Fitted with up to five radios and folding workbench, fitted mapboard and an enclosed annex for use in the vehicles stationary role as a command post. The vehicle will have a crew of six including commander, driver and four radio operators.

This could be fitted with various systems including a high-pressure hose fed by an onboard water tank for crowd control.

This would have a stabilised mast-mounted sensor package comprising thermal imager, radar, TV camera, laser range-finder and operators console inside of the vehicle. This model would have a crew of four.

This is fitted to allow the crew to remain closed up for long periods of time in comfort and provides airfield communication equipment and provision for a concealed weapon. It would normally have a crew of four.