Appeals by two men jailed for using Facebook to try to incite disorder during August's riots in England have been rejected by the Court of Appeal.
Perry Sutcliffe-Keenan, 22, and Jordan Blackshaw, 21, were among 10 people challenging riot-related sentences.
At a 27 September hearing, the pair's lawyers argued that their four year sentences were "manifestly excessive".
The court rejected five other appeals but cut the sentences for three people convicted of handling stolen goods.
The Lord Chief Justice, Lord Judge, sitting with Sir John Thomas and Lord Justice Leveson at the Court of Appeal in London, read the judgements.
'Utterly shocking' lawlessness
Upholding the jail terms given to Blackshaw and Sutcliffe-Keenan, the Lord Chief Justice said the men had used technology for crime - and it was wrong to suggest their offences had been minor simply because they had not gone door-to-door encouraging people to riot.
"It is a sinister feature of these cases that modern technology almost certainly assisted rioters in other places," he said. "What both these appellants intended was to cause very serious crime. All this was incited at a time of sustained countrywide mayhem.
"The (sentencing) judge was fully justified in concluding that deterrent sentences were appropriate. These offenders were caught red-handed."
Blackshaw, from Northwich in Cheshire, and Sutcliffe-Keenan, from Warrington, both pleaded guilty to an offence under the Serious Crime Act 2007, which carried a maximum sentence of 10 years imprisonment.
Blackshaw admitted encouraging others to commit riot, burglary and criminal damage in Northwich, and Sutcliffe-Keenan pleaded guilty to encouraging others to commit riot in Latchford near Warrington, although there were no outbreaks of disorder in either case.
As well as the Facebook appeals, the court rejected five appeals against sentence by looters jailed for burglary.
Lord Judge said the level of lawlessness during the riots "was utterly shocking and wholly inexcusable".
"The imposition of severe sentences, intended to provide both punishment and deterrence, must follow.
"It is very simple. Those who deliberately participate in disturbances of this magnitude, causing injury and damage and fear to even the most stout-hearted of citizens, and who individually commit further crimes during the course of the riots are committing aggravated crimes. They must be punished accordingly and the sentences should be designed to deter others," he said.
"The offenders were deriving support and comfort and encouragement from being together with other offenders, and offering comfort support and encouragement to the offenders around them."
Lord Judge said the "sheer numbers involved" may have led some to believe they would escape detection.
BBC home affairs correspondent Dominic Casciani says the judgements pave the way for judges across England to impose tough jail sentences in cases yet to come to court.
- Stephen Craven, 24, of Salford, jailed for 12 months after pleading guilty to handling stolen goods - sentence halved to six months
- Stephen Carter, 26, of James Street, Salford, Greater Manchester, who was caught with a bag of clothes and shoes worth £500 and jailed for 16 months for theft by finding - sentenced halved to eight months
- Coach driver David Beswick, 31, of Anson Street, Eccles, jailed for 18 months for handling stolen goods - sentenced halved to nine months
- Jordan Blackshaw, 21, of Northwich, Cheshire, jailed for four years after admitting encouraging a riot on Facebook, which never happened
- Perry Sutcliffe-Keenan, 22, of Warrington, Cheshire, jailed for four years after admitting encouraging a riot on Facebook, which never happened
- Chef Enrico Vanasco, 25, jailed for 20 months after admitting burglary relating to a £300 camera
- Hassan Halloway, 39, of Bennett Street, Crumpsall, who was jailed for four years and eight months after admitting burglary charges and violent disorder
- Territorial Army soldier Lorraine McGrane, 19, from Peckham, south-east London, jailed for 13 months after admitting stealing a television
MPs, legal figures and justice campaigners have previously argued that disproportionate sentences have been handed down for riot-related offences.
Violence broke out in the north London district of Tottenham in August after a protest over the fatal police shooting of local man Mark Duggan.
Between 6 and 9 August, the disorder spread to several other English cities, including Birmingham, Manchester and Nottingham. Shops were looted, buildings burned and the deaths of five people have been linked to the rioting.