Rajapaksa became the Chair of the Commonwealth after hosting the Commonwealth Summit in November in the country.
Foreign Minister G L Peiris represented Sri Lanka at the celebration in London yesterday.
Although no reasons were given for Rajapaksa's absence, his last two visits to the British capital were marked by demonstrations by the pro-LTTE diaspora.
Another irritant was a resolution co-sponsored by the UK in the UN Human Rights Council against Sri Lanka that called for rights accountability and reconciliation with minority Tamils.