GC London extension island platform length

[Helmdon]

I had some drawings somewhere but can’t find them... can anyone please let me know (preferably in mm) how long a London extension platform should be in OO - Helmdon for preference?

 

Nearly went and measured it myself earlier today but it’s vanishing rapidly under tree cover!

 

thanks to anyone that can help

[Butler Henderson]

Rothley is 441ft and all were built to the same general format   -  1764mm in 4mm scale 

[Nick Holliday]

There is a very useful, and accurate, measurement tool on the NLS maps site. Here's Brackley, at 461 feet,  1844 mm in 4mm.  Helmdon appears to be similar, but the presence of the road bridge makes it difficult to tell where the platform ends.

OS Map from NLS

[Helmdon]

6 hours ago, Nick Holliday said:

There is a very useful, and accurate, measurement tool on the NLS maps site. Here's Brackley, at 461 feet,  1844 mm in 4mm.  Helmdon appears to be similar, but the presence of the road bridge makes it difficult to tell where the platform ends.

OS Map from NLS

thanks - close enough for my my purposes. Helmdon was a standard LE island station so the platform ends under the bridge!