In this paper, we present a novel, ultra-long-time-constant analog integrator circuit as part of an analogue signal processing block. By employing transconductance reduction techniques a time constant of up to 5s is achievable using only a 35pF capacitor. This is achieved by introducing a R-2R current divider network in the feedback loop, additionally allowing the transconductance to be digitally-tuned within a range of 0.2 to 5 seconds to 4-bit resolution. Furthermore, through internal compensation, the clockless integrator achieves a temperature dependance of under 1.2\% over the 0$^oC$ to 100$^oC$ range.