Consider this first and do not be influenced either way by the paintwork. A sound car can look terrible if the paint is shabby through oxidation, efflorescence or peeling, conversely a shiny finish in an attractive colour can look most alluring. There will always be those who invest in a tin or three of filler and a quick blow over for a fast buck. Look at the fit of the doors, boot lid and bonnet. Alvises had narrow, even panel gaps when new and if they are still like that it augers well for the state of the important bits underneath. If the door fits closely at the top but tends to spring out at the bottom then beware - this often indicates rot in the wood frame and/or the metal flange screwed to it over which the outer panel is folded. This type of deterioration is common and very labour intensive to rectify.
Check all the doors - examine the locks and see if they are secure, also the catch plates on which they engage. Look for any looseness indicating that the wood into which they are screwed has rotted. Push and pull hard on the door handles to see if the pillar moves in and out, betraying decay in the body frame. Open the door and lift it upwards from the bottom as far away as possible from the hinges - this will reveal wear and looseness in the hinges in double quick time and indicate the degree to which the door has dropped. (Be careful as it is not unknown for doors to come off given this treatment, or for the bottom of the pillar to come away.) On pre-war saloons give the top of the windscreen pillar a generous transverse shove with your shoulder - any movement here is bad news.
Push on the top rear of the scuttle side also to check the soundness of its frame. The fit of the doors reveals most about the soundness of a concealed wooden frame. It is surprisingly common for the whole door pillar to disappear and the various screw nails to be threaded into thin air, held in by a film of their own rust. Check the panelling all over for the tell-tale bubbling which indicates corrosion underneath. This need not be serious, especially if the body is alloy panelled, but on a steel body rust holes are sure to be found underneath. Cracks frequently start at the corners of the boot aperture on aluminium panelled cars as a result of metal fatigue, the pillars at the side of the windscreen being another favourite area.
Look for disturbance in the paint, a sure sign that the frame is moving and will need attention. Over the years the steel mudguards on pre-war cars tend to become very thin and their stays rot through, allowing them to flap around, increasing the rate of deterioration. Check for rust along the part where they are screwed into the back wheel arches, and where they meet the bonnet sides. Get down and sight along the surface of the panels from all four corners and along the roof. Look for the ripples which indicate filler concealing damage, and panels which do not sit in line with their neighbours, the result of accident damage or structural defects. Remember that aluminium is a soft metal, and dents easily, so some ripples may simply be the result of minor contusions over the years.
Sunroofs are troublesome fittings, although the fabric covered pre-war efforts are easier to repair than the later metal ones, they are often found plated over. Rot often stems from blocked or degenerate drains on the sunroof, and can appear a long way away from the point of entry of the water. Webasto roofs are encountered fairly frequently on the Park Ward saloons, opinions vary as to their desirability.
Dropheads bring their own little problems. Check that the hood does actually open and shut .They are prone to rattle and leak unless in perfect order.
The glass windows in many dropheads are large and heavy. This strains the regulator mechanisms which often give up the ghost and are difficult to repair. Mulliners went over to the extensive use of cast aluminium for door frames and pillars on the TA 21 and its derivatives, making these bodies really strong and durable. Wood was however used for the rear frames and these can rot, as can the steel boot floor. Wings are steel and rust at their lower edges, the back ones at the top too where they are attached to the wood frame with sundry woodscrews. Generally these are excellent bodies to restore, and because, one suspects, of their staid appearance, they are much cheaper than the later Park Ward cars. The Tickford dropheads are much more sought after than the corresponding saloons, but use a complex wood frame which is tricky to get right during a restoration.
The Park Ward bodied Three Litres often suffer from rust and need special comment. Roof, bonnet, boot lid and, Series II onwards, doors, are alloy and normally last well, but everywhere else is suspect. These bodies achieve lightness and strength through being made of a complex set of thin steel pressings joined by the then new technique of spot welding. Corrosion protection was negligible and water got in through the porous gaps between the welds, promoting rampant rust in the invisible and inaccessible sections inside. Lift the carpet in the boot and examine the floor behind the wheel arches and in the tool recess at the back. The spare wheel is in a tray under the boot. This and the petrol tank straps rust badly. Check if the wheel tray can be lowered and raised, (without using a jack!).
Examine the inside of the rear wings on either side, underneath the car at the back. The boot floor should extend downwards as a flange on either side to meet the outer wings about halfway down, forming a box like structure, strong and light. They may well be very rusty or rotted away. When they rot the whole back end moves down and out, until it rests on the rear chassis extensions.
Incidentally jacking the car using the makers' jack is not recommended, the jacking tubes are liable to come off and the jack itself is not strong. If either breaks, there is a loud bang and the car crashes down! Use a trolley or bottle jack under the axle, or the cross member at the front.
The roof panel on saloons has thin wood framing attached at the bottom corners of the back window to a large wooden cross member with three lightening holes running at the back of the parcel shelf. Expect rot here as water invariably gets in at these points. Frequently the roof panel is only held on by gravity at the back - this can be demonstrated by kneeling on the back seat and pushing upwards with your shoulders. Remove the rear seat cushion and look for damp and rot where the base panel meets the side vertical parts. Loose leather trim is a giveaway - the metal it was once glued to has rusted away. The back wings should be attached to the inner wheel arch - grasp the panel at the apex above the wheel and observe how much the sheet metal running to the back flexes - it shouldn't move at all.
Examine the door sills - the outer part is thin and easy to replace, but further in and underneath is a plethora of often rusty spot welded bracketry which is neither easy nor cheap to fix. This is especially true of the nearside, here the brake servo and its vacuum reservoir are located on the disc braked cars, this reservoir corrodes unseen until it collapses. Right at the front on these models are two brackets attaching the front panelling to the chassis, and these can rust away, leaving the front end unsupported. On the TE and TF cars, the twin headlight assemblies harbour untold amounts of accumulated damp road dirt, causing rapid deterioration of the thin metal. Fortunately almost all the panels are available, but they are far from cheap, and it is best to be prepared for a complete body rebuild from the outset. On these cars it is quite difficult to achieve perfect panel alignment, especially along the sides. The front wings often tend to gape outwards at the back of the wheel arches when the body should be "straight" from the back of the door to the very front.
Many cars have been well restored, and are honestly presented by their vendors, but there are also many out there which look great, have long MOT certificates and drive well, yet are partially rotten underneath. The prices may well be identical. The warning is repeated: Caveat emptor!