  Double and triple ionization of allene are investigated using
electron-electron, ion-ion, electron-electron-ion and electron-electron-ion-ion
(ee, ii, eei, eeii) coincidence spectroscopies at selected photon energies. The
results provide supporting evidence for a previously proposed roaming mechanism
in H$_3^+$ formation by double ionisation. The lowest vertical double
ionization energy is found to be 28.5 eV, while adiabatic double ionisation is
not accessed by vertical ionisation at the neutral geometry. The triple
ionization energy is found to be close to 50 eV in agreement with theoretical
predictions. The doubly charged parent ion is stable up to about 2 eV above
threshold, after which dissociations by charge separation and by double charge
retention occur with comparable intensities. Fragmentation to H$^+$ +
C$_3$H$_3^+$ starts immediately above threshold as a slow (metastable) decay
with 130+/-10 ns mean lifetime.
