Wikipedia pages
Red telephone boxes (K1-K8)
KX series telephone boxes
Useful links
BT website
BT phone box call charges (cash)
BT phone box call charges (credit/debit card)
0800 REVERSE call charges (land line)
0800 REVERSE call charges (mobile)
BT phone box fault reports
BT phone box serviceability
BT phone box adoption
K6 phone box 80th birthday in 2016
Parliamentary debate on public telephones, 12 October 2004
Debate in the Scottish Parliament, 28 June 2017
The Hasbi Report Universal Service Obligations and Public Payphone Use: Is Regulation Still Necessary in the Era of Mobile Telephony?
Government guide to call charges and phone numbers. This does not apply to phone boxes. See "BT phone box call charges" (above) for these.
Video by Tom Scott about conversion of phone boxes to defibrillator use, and how to use the defibrillators https://www.youtube.com/watch?v=ecVHYg4_vZw