Steed's Cars - Vauxhall

"The Vauxhall 30-98, one of the greatest sports cars of the twentieth century and the first in the UK to top 100mph in production form."

According to the Vauxhall official website this car was developed in only 71 days and had a "4,525cc side-valve four-cylinder engine, producing 90bhp." The Vauxhall was made in two basic types, E-type and the more powerful OE-type, built between 1923 and 1927.

According to the Motorsportmagazine from 1946 it had this specifications:

"The above generally covers the specification of the OE engine, which can be summed up as follows: -

Number of cylinders ... Four.
Bore ... 98mm/ (3 5/16 in. or 3.9375 in.).
Stroke ... 140 mm. (5 19/32 in. or 5.59375 in.).
Maximum b.h.p. ... 112
Maximum r.p.m. ... 3,400
Compression ratio ... 5.2 to 1
Area of piston ... 12.177 sq. in.
Total swept volume ... 272
Torque at 3,400 r.p.m. ... 175 lb. ft.
B.M.E.P. ... 95.8 ln./sq/in.
Max. piston speed ... 3,170 ft./min. at 3,400 r.p.m.
R.A.C. rating ... 23.8 h.p"

Drawing of the plan and side elevation of the standard OE 30/98 Vauxhall chassis on
Drawing of the chassis on
1924 Vauxhall OE Type 30/98

4-seater open tourer
(official: 30/98 hp Vauxhall-Velox sporting car)

License plate is: XT 2276

Colour of the car: aluminium bonnet and dark blue body

The Vauxhall appears in two episodes of series 4:

The Gravediggers
The Thirteenth Hole
The car was first registered on 2 May 1924 and still registered in 1998.

Only 313 cars were manufactured by Vauxhall between 1921 - 1927.
(First) owner of the car was J.C. Bentell, Esquire.
The Vauxhall  (like some of his  Bentleys) has the handbrake on the outside of the driver's car door; therefore Steed can't open the driver's door.
I found color drawings of "Steed's car" made by James Leech in the book:
Classic Cars in profile. Volume 2, ed.Anthony Harding, Profile Publications Ltd. 1967, p.95