Can anybody tell me what this coach is

The first coach behind Flying Scotsman in this picture



and the last coach on this train



Thanks very much

Colin

It maybe  is the dynamometer carriage.

Or some type of inspection saloon?

It is Inspection saloon / observation car No. 41, built in 1892 at Wolverton by the London & North Western Railway, originally West Coast Joint Stock 3rd Class Kitchen dining car No. 484.

A better photo of it here:
http://www.tracksthroughgrantham.uk/recording-the-railway/grantham-railway-galleries/flying-scotsmans-stopover-at-grantham/

It still exists with WCRC, but the observation platform has been rebuilt enclosed such that it is sometimes mistaken for a DMU vehicle...
http://www.cs.rhrp.org.uk/se/CarriageInfo.asp?Ref=652

Thanks, PLD. 

That 1973 story is interesting. A4 Sir Nigel Gresley was stabled a mile from where I lived at the time, and Sunderland won the FA cup.

Seems like yesterday. 

Are you thinking of building one, nookfield?

Thank you very much for the reply and the links.

It looks far to complicated for me to scratch build, but as my skills progress you never know!