[Thread] A brief history of a modern 155mm gun development for the Royal Navy: The 155 TMF. 
In 2004 details emerged of a low risk plan to develop a naval 155mm gun system, which was intended to offer a significant enhancement to the range and lethality of RN Naval Fires, ultimately across a spectrum of Surface and Land targets.
This would be known as as the 155mm Third Generation Maritime Fire Support, or 155 TMF for short.
At the time, the Royal Navy was operating the 4.5" Mk.8 across the Type 22, Type 23 and Type 42 fleets.
The Type 45 was still in development with both the Mk.8 and the (pre-BAE buyout) United Defense Mk.4545 Mod 4 127 mm/54-cal as the main considerations for Naval Fires armament.
155 TMF was to be offered as an alternative to both the Mk.8 4.5" and the Mk.45 5" either as a direct replacement or as a later update to a fitted Mk.8 with other vessels in the fleet refit to a common 155mm system.
155 TMF combined the 155mm gun system used in the Army's AS90 SPG with the RN's existing Mk.8 Mod 1 4.5" gun mounting. The longer Braveheart program 155mm/52-cal barrel would be used. Ordnance would be adapted, automated rammer adjusted and environmental modifications made.
Standard ordnance adapted for automated naval use was to be used initially, however rocket assisted and guided munitions were planned for. What we recognise now as Excalibur and Vulcano would be used alongside conventional unguided munitions to engage surface and land targets.
Work would continue as part of the active Future Surface Combatant program, which would deliver Type 26 and eventually de facto deliver the Type 31 as well as the River Batch 2's.
In 2008, work was underway on the prototype with land firing planned the following year. FSC was now GCS. Delivery to the Fleet, likely starting with Type 45 due to GCS delays, was planned for 2014.
The 155 TMF program was cancelled in 2010 as part of the SDSR 2010. The Financial Crisis, a lack of funds in the Treasury and the constant drain of UOR after UOR plastering over poor procurement decisions to prop up Operations in Iraq and Afghanistan had taken its toll.
In 2012, BAE proposed a very similar concept to the US Navy in order to bring 155mm Naval Fires to the wider DDG-51 fleet rather than just the DDG-1000 fleet. Called AGS-Lite (AGS-L) this was not the same system as the 155 TMF instead sporting a reduced AGS gun on a Mk.45 mount.
Epilogue: Since the cancellation of 155 TMF there has been a shift in RN thinking on Naval Fires with a move to 57mm as the main gun for Type 31. If 155 TMF was driven with an "Enduring need for Naval gun capability identified" what is the future of Naval Fires in the RN?
/FIN
*Mk.45
