Ultrafast laser micromachining has emerged as an excellent tool for fabrication of microstructures in different dielectrics and crystals using pico and femtosecond pulses thanks to the non-linear absorption processes involved in the radiation-matter interaction, such as multiphoton absorption and avalanche ionisation [1]. Recently, non-conventional beams such as Bessel beams, which are characterised by an elongated focal region as opposed to the Gaussian beams with short focus, have been used for in-bulk modification of different transparent materials without the need for sample translation [2]. Diamond is widely used in high energy particle detectors, integrated photonic chips and microfluidic systems due to extreme hardness, high thermal conductivity, biocompatibility and top-notch chemical resistivity [3].